**Exhibit4.50****Standard Stock Purchase Plan****of Converium Holding AG, Zug, Switzerland**December 2006**1** **Introduction** 1.1 The Converium Stock Purchase Plan (the “**Plan**”) is an incentive scheme of ConveriumHolding AG, Zug, Switzerland (the “**Company**”). 1.2 The Plan shall provide an increased incentive for selected employees and members of the boardof directors (the “**Board of Directors**”) of the Company and of its subsidiaries to contributeto the future success and prosperity of the Company, which will enhance the value of the stockof the Company for the benefit of the Company’s shareholders and increase the ability of theCompany to attract and retain employees of exceptional skill and experience. 1.3 The Plan shall provide these employees and members of the Board of Directors an opportunityto obtain shares of the Company (the “**Shares**”). 1.4 All rights and obligations of the participant(s) in the Plan (the “**Participant(s)**”) are asdescribed in these terms and conditions of the Plan. **2** **Participation in the Plan** 2.1 Eligible Participants of this Plan are generally Employees (as defined below) as well asmembers of the Board of Directors. Participants will be determined by the Nomination andRemuneration Committee of the Board of Directors (the “**Committee**”) and/or other bodies of theConverium group.   For the purposes of this Plan, the expression “**Employee**” shall mean a Participant who isemployed for 50 per cent or more of a full employment (and who is not an employee with anhourly wage) by the Company, a company directly or indirectly controlled by the Company(or any other company or business as determined by the Committee in its absolutediscretion), provided, however, that on the relevant date, no notice of termination hasbeen given or termination agreement concluded in respect of the employment agreement ofsuch Employee, other than as provided for in Section 7.2.3. A transfer of an Employee fromthe Company or an affiliated company to theCompany or another affiliated company, and a leave of absence, duly authorized in writingby the relevant employer, for military service or sickness, or for any other purposeapproved by the Committee shall not be deemed a termination of employment unlessemployment is terminated during such leave of absence.         1/5
 

 
2.2 The holding of one of the positions mentioned in clause 2.1 shall grant no right toparticipate or to a continued participation in the Plan or to employment with the Company or asubsidiary of the Company. The Committee shall have full discretion to elect persons otherthan those mentioned in clause 2.1 as Participants. **3** **Offering Periods** 3.1 Depending on the Plan, offerings of Shares are scheduled to take place once or twice ayear, generally for periods of one month. The offering periods, the number of Shares that maybe purchased or the amount that may be invested by a Participant and the purchase price perShare will be determined by the Committee and/or other bodies of the Converium group andcommunicated to the relevant Participants through electronic or other means (the “**GrantNotice**”). 3.2 The Grant Notice shall also set forth the other terms and conditions of the offering ofShares which are not specified in this Plan. In the event of any discrepancy between the termsand conditions of the Grant Notice and those of this Plan, the terms and conditions of theGrant Notice shall prevail. **4** **Purchase Price for Shares**   The purchase price per Share (the “**Purchase Price**”) will be as set forth in theGrant Notice and shall in general correspond to the closing price of the Shares on the SWXSwiss Exchange on or about the date of the Purchase Notice or the closing price of theShares on the SWX Swiss Exchange on the beginning and/or end of the respective offeringperiod. **5** **Purchase of Shares** 5.1 In order to purchase Shares, Participants will have to complete and send to the planadministrator appointed by the Committee (the “**Plan Administrator**”) a purchase notice (the“**Purchase Notice**”). Upon receipt of the duly completed Purchase Notice by the PlanAdministrator, the purchase of the respective Shares will become binding on and irrevocable bythe Participant. 5.2 Unless provided for differently in the Purchase Notice, the Participant shall, at the time ofsending the Purchase Notice, transfer the Purchase Price to the bank account indicated in thePurchase Notice. If the purchase and/or the delivery of the Shares is, at the time ofpurchase, subject to stamp duty, similar tax or levy, the Participant shall, simultaneouslywith the transfer of the Purchase Price, also transfer theamount necessary to pay such stamp duty, similar tax or levy. The Plan Administrator willinform the Participants from time to time accordingly. **6** **Delivery of Shares** 6.1 The Shares will be delivered as soon as possible after receipt by the Plan Administrator         2/5
 

 
** ** of the Purchase Notice and with all rights (such as dividend rights) pertaining tosuch Shares on the date of delivery. Delivery on that date is conditional upon receipt bythe Plan Administrator of a duly completed Purchase Notice and the Purchase Priceapplicable to the Shares purchased (as well as stamp duty, similar tax or levy, if any). 6.2 The Shares will be delivered to the securities account of the Participant opened with thePlan Administrator or its correspondent bank. **7** **Vesting Period** 7.1 The right to the Shares is conditional upon the Participant being an Employee on thedates specified in the Grant Notice under “Vesting”. 7.2 Disregarding the provisions of Section 7.1, the right of a Participant to the Shares shallbecome unconditional at the time one of the following events occurs: 7.2.1 Normal retirement of the Participant;  7.2.2 permanent disability of the Participant, as determined by the Company, ordeath of the Participant;  7.2.3 termination of employment based on grounds for which the employer of theParticipant, the Company and/or any of its subsidiaries are solely responsible;  7.2.4 transfer of a Participant from the Company or an affiliated company to theCompany or another affiliated company in another tax jurisdiction, if the Committeedecides, in its sole discretion, that the right of a Participant to the Options shallbecome unconditional.**8** **Adjustment of the Plan** 8.1 In the event of a Potential Adjustment Event (as defined below), the Board of Directorsshall, if deemed necessary by the Board of Directors, adjust the rights under the Plan, byapplying adjustment methods customary in the market at that time. For the purposes hereof, a“**Potential Adjustment Event**” includes: 8.1.1 a sub-division, consolidation or reclassification of the Shares;  8.1.2 a grant or distribution to existing holders of Shares of subscription orother rights for the acquisition of Shares or other securities or rights granting theright to payment of dividendsand/or the proceeds of liquidation of the Company, in any case for free or forpayment (cash or other) at less than the prevailing market price as determined bythe Committee;  8.1.3 a reduction of the share capital or of other securities or rights grantingthe right to payment of dividends and/or the proceeds of liquidation of the Company(in any case by way of a cancellation of Shares or such other securities or rights);  8.1.4 any similar event that may have a diluting or concentrative effect on themarket value of the Shares;         3/5
 

 
 8.1.5 a consolidation, amalgamation or merger of the Company, in which the Companyis not the continuing corporation;  8.1.6 a sale by the Company of all or substantially all of its business and / or assets toa person or entity which is not a wholly-owned subsidiary of the Company;8.2  In the event of a Potential Adjustment Event, the Board of Directors shall also have theright to terminate the Plan and compensate Participants with unvested Shares with such cash orother compensation to the Participants as the Board of Directors shall determine in its solediscretion.8.3  Any Additional Taxes (as defined below) that may be imposed on the Participant as a result ofsuch a modification and/or, following such modification, a purchase of Shares, shall be borneby the Company. In this context, “**Additional Taxes**” means such taxes, social contributionsand similar duties in excess of those which would have been borne by the Participant absentsuch a modification.**9** **Take-over situation**1Upon the occurrence of a Take-over Situation (as defined below) all outstanding Sharesgranted shall immediately vest. For the purposes hereof, a “Take-over Situation” shall mean theconclusion of a binding tender offer for more than 33 1/3 per cent of the total voting power(whether exercisable or not) of the Company by a person (or two or more persons acting in concert),provided that the conditions, if any, for such offer have been met or waived.**10** **Taxes / Social Security / Brokerage Fees** 10.1 All taxes, duties and similar charges imposed or levied in connection with thepurchase, holding and transfer of Shares, such as stamp duties, value added taxes, directtaxes of the Participant (excluding direct taxes imposed on the Company or the relevantemployer), will be payable by the Participant. 10.2 Unless provided for differently in the Grant Notice, all payments on account of socialinsurance, pension fund or similar contributions to be made in connection with the purchase orholding of Shares as a result of such purchase and the transfer or disposal of Shares acquiredthrough the purchase of Shares pursuant to this Plan will be payable by the Participant. 10.3 All brokerage fees charged by the Plan Administrator in connection with the purchase ofShares in accordance with Section 5 and the transfer of such Shares to the account of theParticipant with the Plan Administrator or its correspondent bank will be borne by theCompany. Brokerage fees andcosts and expenses related to a later transfer or sale of such Shares will be borne by theParticipant. 1 inserted April 20, 2004/amended by NRC on November 29, 2006         4/5
 

 
**11** **Transfer Restriction**   The rights and potential rights granted under the Plan may not be transferred orpledged by the Participant, except that the Board of Directors, in its absolutediscretion, may permit a transfer or pledge thereof, which transfer or pledge shall becomeeffective only upon registration thereof in the relevant register. **12** **No Segregation**   The Company will not and shall not be required to segregate any Shares or any cashwhich may at any time be used for the purposes of this Plan and the Plan shall constitutean unfunded plan of the Company. **13** **Amendment and Administration of the Plan** 13.1 The Board of Directors shall have the right to amend or terminate the Plan or to decideon modifications thereof in a particular case at any time. On termination, the Plan remainsapplicable to rights or potential rights to Shares existing at that time unless such rights orpotential rights are terminated by the Board of Directors at the same time. 13.2 Unless provided for differently in this Plan, decisions with respect to this Plan shall betaken by the Committee who shall delegate administrative functions to the Plan Administrator. 13.3 The Plan Administrator shall administer the Plan and maintain a register setting out, interalia, the details of each Participant and the number of vested and unvested Shares to whichsuch Participant is entitled to, showing their vesting date and Purchase Price. 13.4 The Plan Administrator shall establish rules and regulations for the administration of thePlan, in particular the purchase of Shares and the sale or transfer of Shares. **14** **Applicable law / jurisdiction** 14.1 **The Plan and the rights granted thereunder shall be subject to and governed by Swisslaw.** 14.2 **Exclusive place of jurisdiction for all disputes arising out of or in connection with thisPlan shall, to the extent legally possible, be the commercial courts of Zurich, Switzerland.** **15** **Acceptance of the Plan**   **By accepting any right or potential right to purchase Shares under this Plan orany related right, the Participant explicitly accepts the terms and conditions of thePlan, in particular the choice of law and jurisdiction clause.**         5/5