Document:

Exhibit 4.2

 

SPECIMEN CLASS A ORDINARY SHARE CERTIFICATE

 

	NUMBER                             	SHARES

 

ARYA SCIENCES ACQUISITION CORP.

INCORPORATED UNDER THE LAWS OF THE
CAYMAN ISLANDS

CLASS A ORDINARY SHARES

 

SEE REVERSE FOR

CERTAIN DEFINITIONS

 

CUSIP [    ]

 

This Certifies that ________________________________________________
is the owner of _______________

 

FULLY PAID AND NON-ASSESSABLE CLASS
A ORDINARY SHARES OF THE PAR VALUE OF $0.0001

 

EACH OF

 

ARYA SCIENCES ACQUISITION CORP. (THE
“COMPANY”)

 

transferable on the books of the Company
in person or by duly authorized attorney upon surrender of this certificate properly endorsed.

 

The Company will be forced to redeem
all of its Class A ordinary shares if it is unable to complete a business combination within the period of time set forth in the
Company’s amended and restated memorandum and articles of association, as the same may be amended from time to time, all
as more fully described in the Company’s final prospectus dated , 2018.

 

This certificate is not valid unless
countersigned by the Transfer Agent and registered by the Registrar.

 

Witness the seal of the Company and the
facsimile signatures of its duly authorized officers.

 

Dated:                   

 

	Secretary	 	[Corporate Seal]

Cayman Islands	 	Chief Executive Officer 
	 	 	 	 	 

 

     

     

    

 

ARYA SCIENCES ACQUISITION CORP.

 

The Company will furnish without charge to
each shareholder who so requests the powers, designations, preferences and relative, participating, optional or other special rights
of each class of shares or series thereof of the Company and the qualifications, limitations, or restrictions of such preferences
and/or rights. This certificate and the shares represented thereby are issued and shall be held subject to all the provisions of
the Company’s amended and restated memorandum and articles of association and all amendments thereto and resolutions of the
Board of Directors providing for the issue of Class A ordinary shares (copies of which may be obtained from the secretary of the
Company), to all of which the holder of this certificate by acceptance hereof assents. The following abbreviations, when used in
the inscription on the face of this certificate, shall be construed as though they were written out in full according to applicable
laws or regulations:

 

	TEN COM	—	as tenants in common	UNIF GIFT MIN ACT	—	
        _______Custodian _____________

            (Cust)                                  (Minor)   

	TEN ENT	—	as tenants by the entireties	 	 	  
	JT TEN	—	as joint tenants with right of survivorship and not as tenants in common	 	 	
        under Uniform Gifts to Minors Act _____________________________

        (State)

 

Additional abbreviations may also be used though not in the
above list.

 

For value received,_____________________hereby sells, assigns
and transfers unto

 

 

(PLEASE INSERT SOCIAL SECURITY OR OTHER
IDENTIFYING NUMBER(S) OF ASSIGNEE(S))

 

 

 

(PLEASE PRINT OR TYPEWRITE NAME(S) AND ADDRESS(ES),
INCLUDING ZIP CODE, OF ASSIGNEE(S))

 

 

 

 

 

 

 

 

 

Shares of the capital stock represented by the within Certificate,
and do hereby irrevocably constitutes and appoints

 

 

 

Attorney to transfer the said stock on the books of the within
named Company with full power of substitution in the premises.

 

Dated: _____________

 

	 	 
	 	Stockholder
	 	 
	 	NOTICE: THE SIGNATURE(S) TO THIS ASSIGNMENT MUST CORRESPOND WITH THE NAME AS WRITTEN UPON THE FACE OF THE CERTIFICATE IN EVERY PARTICULAR, WITHOUT ALTERATION OR ENLARGEMENT OR ANY CHANGE WHATEVER.

 

     

     

    

 

Signature(s) Guaranteed:

 

By

 

		 
	 	 
	 	 

 

THE SIGNATURE(S) MUST BE GUARANTEED BY AN ELIGIBLE GUARANTOR
INSTITUTION (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE
MEDALLION PROGRAM, PURSUANT TO S.E.C. RULE 17Ad-15 OR ANY SUCCESSOR RULE).

 

In each case, as more fully described in the Company’s
final prospectus dated                  ,
2018, the holder(s) of this certificate shall be entitled to receive a pro-rata portion of certain funds held in the trust account
established in connection with its initial public offering only in the event that (i) the Company redeems the Class A ordinary
shares sold in its initial public offering and liquidates because it does not consummate an initial business combination within
the period of time set forth in the Company’s amended and restated memorandum and articles of association, (ii) the Corporation
redeems the Class A ordinary shares sold in its initial public offering in connection with a shareholder vote to amend the Company’s
amended and restated memorandum and articles of association to modify the substance or timing of the Company’s obligation
to redeem 100% of the Class A ordinary shares if it does not consummate an initial business combination within the time period
set forth therein, or (iii) if the holder(s) seek(s) to redeem for cash his, her or its respective Class A ordinary shares in connection
with a tender offer (or proxy solicitation, solely in the event the Company seeks shareholder approval of the proposed initial
business combination) setting forth the details of a proposed initial business combination. In no other circumstances shall the
holder(s) have any right or interest of any kind in or to the trust account.Exhibit 4.3

 

[Form of Warrant Certificate]

 

[FACE]

 

Number

 

Warrants

 

 

 

THIS WARRANT SHALL BE VOID IF NOT EXERCISED
PRIOR

TO THE EXPIRATION OF THE EXERCISE PERIOD PROVIDED FOR

IN THE WARRANT AGREEMENT DESCRIBED BELOW

 

ARYA SCIENCES ACQUISITION CORP.

 

A Cayman Islands Exempted Company

 

CUSIP [●]

 

Warrant Certificate

 

This Warrant Certificate certifies
that                , or registered assigns,
is the registered holder of                  
warrant(s) evidenced hereby (the “Warrants” and each, a “Warrant”) to purchase
shares of Class A ordinary shares, $0.0001 par value (“Ordinary Shares”), of ARYA Sciences Acquisition
Corp., a Cayman Islands exempted company (the “Company”). Each Warrant entitles the holder, upon exercise
during the period set forth in the Warrant Agreement referred to below, to receive from the Company that number of fully paid and
non-assessable Ordinary Shares as set forth below, at the exercise price (the “Exercise Price”) as determined
pursuant to the Warrant Agreement, payable in lawful money (or through “cashless exercise” as provided
for in the Warrant Agreement) of the United States of America upon surrender of this Warrant Certificate and payment of the Exercise
Price at the office or agency of the Warrant Agent referred to below, subject to the conditions set forth herein and in the Warrant
Agreement. Defined terms used in this Warrant Certificate but not defined herein shall have the meanings given to them in the Warrant
Agreement.

 

Each Warrant is initially exercisable for
one fully paid and non-assessable Ordinary Share. The number of Ordinary Shares issuable upon exercise of the Warrants is subject
to adjustment upon the occurrence of certain events set forth in the Warrant Agreement.

 

The initial Exercise Price per Ordinary Share
for any Warrant is equal to $11.50 per share. The Exercise Price is subject to adjustment upon the occurrence of certain events
set forth in the Warrant Agreement.

 

Subject to the conditions set forth in the
Warrant Agreement, the Warrants may be exercised only during the Exercise Period and to the extent not exercised by the end of
such Exercise Period, such Warrants shall become void.

  

     

     

    

 

Reference is hereby made to the further provisions
of this Warrant Certificate set forth on the reverse hereof and such further provisions shall for all purposes have the same effect
as though fully set forth at this place.

 

This Warrant Certificate shall not be valid
unless countersigned by the Warrant Agent, as such term is used in the Warrant Agreement.

 

This Warrant Certificate shall be governed
by and construed in accordance with the internal laws of the State of New York, without regard to conflicts of laws principles
thereof.

 

	 	ARYA SCIENCES ACQUISITION CORP. 
	 	 	 
	 	By:	 
	 	 	Name: 
	 	 	Title:
	 	 	 
	 	CONTINENTAL STOCK TRANSFER & TRUST COMPANY, as Warrant Agent
	 	 	 
	 	By:	 
	 	 	Name:
	 	 	Title:

 

     

     

    

 

[FORM OF WARRANT CERTIFICATE]

[REVERSE]

 

The Warrants evidenced by this Warrant Certificate
are part of a duly authorized issue of Warrants entitling the holder on exercise to receive Ordinary Shares and are issued or to
be issued pursuant to a Warrant Agreement dated as of [●], 2018 (the “Warrant Agreement”), duly
executed and delivered by the Company to Continental Stock Transfer & Trust Company, a New York corporation, as warrant agent
(the “Warrant Agent”), which Warrant Agreement is hereby incorporated by reference in and made a part
of this instrument and is hereby referred to for a description of the rights, limitation of rights, obligations, duties and immunities
thereunder of the Warrant Agent, the Company and the holders (the words “holders” or “holder”
meaning the Registered Holders or Registered Holder) of the Warrants. A copy of the Warrant Agreement may be obtained by the holder
hereof upon written request to the Company. Defined terms used in this Warrant Certificate but not defined herein shall have the
meanings given to them in the Warrant Agreement.

 

Warrants may be exercised at any time during
the Exercise Period set forth in the Warrant Agreement. The holder of Warrants evidenced by this Warrant Certificate may exercise
them by surrendering this Warrant Certificate, with the form of election to purchase set forth hereon properly completed and executed,
together with payment of the Exercise Price as specified in the Warrant Agreement (or through “cashless exercise” as
provided for in the Warrant Agreement) at the principal corporate trust office of the Warrant Agent. In the event that upon any
exercise of Warrants evidenced hereby the number of Warrants exercised shall be less than the total number of Warrants evidenced
hereby, there shall be issued to the holder hereof or his, her or its assignee, a new Warrant Certificate evidencing the number
of Warrants not exercised.

 

Notwithstanding anything else in this Warrant
Certificate or the Warrant Agreement, no Warrant may be exercised unless at the time of exercise (i) a registration statement covering
the Ordinary Shares to be issued upon exercise is effective under the Securities Act and (ii) a prospectus thereunder relating
to the Ordinary Shares is current, except through “cashless exercise” as provided for in the Warrant Agreement.

 

The Warrant Agreement provides that upon
the occurrence of certain events the number of Ordinary Shares issuable upon exercise of the Warrants set forth on the face hereof
may, subject to certain conditions, be adjusted. If, upon exercise of a Warrant, the holder thereof would be entitled to receive
a fractional interest in an Ordinary Share, the Company shall, upon exercise, round down to the nearest whole number of Ordinary
Shares to be issued to the holder of the Warrant.

 

Warrant Certificates, when surrendered at
the principal corporate trust office of the Warrant Agent by the Registered Holder thereof in person or by legal representative
or attorney duly authorized in writing, may be exchanged, in the manner and subject to the limitations provided in the Warrant
Agreement, but without payment of any service charge, for another Warrant Certificate or Warrant Certificates of like tenor evidencing
in the aggregate a like number of Warrants.

 

     

     

    

 

Upon due presentation for registration of
transfer of this Warrant Certificate at the office of the Warrant Agent a new Warrant Certificate or Warrant Certificates of like
tenor and evidencing in the aggregate a like number of Warrants shall be issued to the transferee(s) in exchange for this Warrant
Certificate, subject to the limitations provided in the Warrant Agreement, without charge except for any tax or other governmental
charge imposed in connection therewith.

 

The Company and the Warrant Agent may deem
and treat the Registered Holder(s) hereof as the absolute owner(s) of this Warrant Certificate (notwithstanding any notation of
ownership or other writing hereon made by anyone), for the purpose of any exercise hereof, of any distribution to the holder(s)
hereof, and for all other purposes, and neither the Company nor the Warrant Agent shall be affected by any notice to the contrary.
Neither the Warrants nor this Warrant Certificate entitles any holder hereof to any rights of a shareholder of the Company.

 

     

     

    

 

ELECTION TO PURCHASE

(TO BE EXECUTED UPON EXERCISE OF WARRANT)

 

The undersigned hereby irrevocably elects
to exercise the right, represented by this Warrant Certificate, to receive Ordinary Shares and herewith tenders payment for such
Ordinary Shares to the order of ARYA Sciences Acquisition Corp. (the “Company”) in the amount of $[●] in
accordance with the terms hereof. The undersigned requests that a certificate for such Ordinary Shares be registered in the name
of [●], whose address is [●] and that such Ordinary Shares be delivered to whose address is [●]. If said number
of Ordinary Shares is less than all of the Ordinary Shares purchasable hereunder, the undersigned requests that a new Warrant Certificate
representing the remaining balance of such Ordinary Shares be registered in the name of [●], whose address is [●] and
that such Warrant Certificate be delivered to [●], whose address is [●].

 

In the event that the Warrant has been called
for redemption by the Company pursuant to Section 6 of the Warrant Agreement and the Company has required cashless exercise
pursuant to Section 6.3 of the Warrant Agreement, the number of Ordinary Shares that this Warrant is exercisable for shall
be determined in accordance with subsection 3.3.1(b) and Section 6.3 of the Warrant Agreement.

 

In the event that the Warrant is a Private
Placement Warrant that is to be exercised on a “cashless” basis pursuant to subsection 3.3.1(c) of the Warrant
Agreement, the number of Ordinary Shares that this Warrant is exercisable for shall be determined in accordance with subsection
3.3.1(c) of the Warrant Agreement.

 

In the event that the Warrant is to be exercised
on a “cashless” basis pursuant to Section 7.4 of the Warrant Agreement, the number of Ordinary Shares that this
Warrant is exercisable for shall be determined in accordance with Section 7.4 of the Warrant Agreement.

 

In the event that the Warrant may be exercised,
to the extent allowed by the Warrant Agreement, through cashless exercise (i) the number of Ordinary Shares that this Warrant is
exercisable for would be determined in accordance with the relevant section of the Warrant Agreement which allows for such cashless
exercise and (ii) the holder hereof shall complete the following: The undersigned hereby irrevocably elects to exercise the right,
represented by this Warrant Certificate, through the cashless exercise provisions of the Warrant Agreement, to receive Ordinary
Shares. If said number of Ordinary Shares is less than all of the Ordinary Shares purchasable hereunder (after giving effect to
the cashless exercise), the undersigned requests that a new Warrant Certificate representing the remaining balance of such Ordinary
Shares be registered in the name of [●], whose address is [●] and that such Warrant Certificate be delivered to [●],
whose address is [●].

 

[Signature Page Follows]

 

     

     

    

 

	Date:                    ,
    20	 	
	 	 	

	 	 	(Signature)
	 	 	 
	 	 	

	 	 	

	 	 	

	 	 	(Address)
	 	 	 
	 	 	

	 	 	(Tax Identification Number)
	 	 	 
	Signature Guaranteed:	 	 
	 	 	 
	
	 	 

 

THE SIGNATURE(S) SHOULD BE GUARANTEED BY AN ELIGIBLE GUARANTOR
INSTITUTION (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE
MEDALLION PROGRAM, PURSUANT TO S.E.C. RULE 17Ad-15 OR ANY SUCCESSOR RULE).

 

[Signature Page to Election to Purchase]

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