Exhibit 4.2


 


	NUMBER	SHARES	 
	 	 
	C	 


 


MONTEREY BIO ACQUISITION
CORPORATION


 


INCORPORATED UNDER THE LAWS
OF THE STATE OF DELAWARE


 


COMMON STOCK


 


SEE REVERSE FOR

CERTAIN DEFINITIONS


 


CUSIP [●]


 


This Certifies that


 


is the owner of


 


FULLY PAID AND NON-ASSESSABLE
SHARES OF COMMON STOCK OF


 


MONTEREY BIO ACQUISITION
CORPORATION


 


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 liquidate if it is unable
to complete an initial business combination as defined in, and within the time period required by, its Amended and Restated Certificate
of Incorporation, as the same may be amended from time to time.




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


Witness the facsimile signatures
of its duly authorized officers.


 


Dated:


 


	 	 	 
	CHAIRMAN	 	CHIEF FINANCIAL OFFICER


 


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	______
	 	TEN ENT –	as tenants by the entireties	 	(Cust)	 	(Minor)
	 	JT TEN –	as joint tenants with right of survivorship	under Uniform Gifts to Minors
	 	 	and not as tenants in common	 	Act ______________
	 	 	 	 	 	(State)	 


 


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


 



     


     


    




 


 Monterey Bio Acquisition Corporation 


 


The Company will furnish without
charge to each stockholder 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 Certificate of Incorporation and all amendments thereto and resolutions of the Board of Directors providing for the
issue of preferred stock (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.


 


For value received, ___________________________
hereby sells, assigns and transfers unto


 


	PLEASE INSERT SOCIAL SECURITY OR OTHER	
	IDENTIFYING NUMBER OF ASSIGNEE	 






 


	 


 


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


 


shares of common
stock represented by the within Certificate, and do hereby irrevocably constitute and appoint


 


 


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


 


	Dated  	                                                                                   	 	 
	 	 	 	 








	 	 
	 	Notice:  	 The signature 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:


 





	 
	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).


 


As more fully described in the Company’s
final prospectus dated as of [•], 2021, the holder of this certificate shall be entitled to receive funds from the trust account
established in connection with the Company’s initial public offering only in the event of the Company’s liquidation upon failure
to consummate a business combination within the required time period set forth in the Company’s Amended and Restated Certificate
of Incorporation as the same may be amended from time to time (the “Certificate”), or if the holder seeks to convert his or
her shares of common stock upon consummation of a business combination or in connection with certain amendments to the Certificate. In
no other circumstances shall the holder have any right or interest of any kind in or to the trust account.