22Y 



and ovate-lanceolate in outline : pallial border stiongly twice inflected: 

 pallial sinus proper very deep, narrow, acutely pointed, extending far 

 into the umbonal cavity, and reaching as far backwards as to within one 

 or two mm. from the tij)s of the beaks; anterior pallial inflection also 

 very deep, but broader and not extending quite so far backwards as the 

 inner termination of the true pallial sinus. 



Dimensions of a specimen which is ovately-orbicular in outline : 

 length, forty-two millimetres, height, thirty-seven and a-half mm. : 

 maximum thickness twenty-three. In an ovately subtrigonal cast of 

 this species the maximum length and height are each fifty mm., and 

 the thickness through the closed valves is thirty-five. 



Bear Skin Bay, Skidegate Inlet : eleven specimens. 



The very deep double inflection of the pallial border appears to be 

 the only point wherein this shell differs from the Thetis major of 

 Sowerby. In other respects the present species seem to be intermediate 

 between the T. minor and the T. major. Some paleontologists, such as 

 F. Ea^mer, E. Forbes, and Mons. Ebray, regard all the nominal spe- 

 cies of Thetis as varieties of one, which Effimer proposes to call T. 

 Sowerbii, and if this view be adopted, the Thetis above described will 

 of coui'se rank only as one of the forms of T. Sowerbii. 



Cyprina occidentalis. (N. Sp.) 



Fig. 10. Cyprina occidentalis. Outline of a castiof a left valve, 



