PLATE XVIII. 



Fig. I. Pscciidomonotis toudstriata. Left valve of type. Postero- 

 ventral portion crushed, probably giving it undue prominence. 

 The striae are finer, and more crinkley than represented in drawing. 

 About natural size. 



Fig. I a. Outline showing convexity of the same. 



Fig. lb. Outline showing the convexity of the adult long- 

 hinged forms. 



Figs, ic and d. Young specimen of the long-hinged form 

 showing different degrees of development of the hinge and ears. 

 About natural size. 



Fig. 2. Pscudomonotis roluista. Left valve of type. The strire 

 are finer and more wavy than represented, and the upper third is 

 practically glabrous, only the faintest traces of stria? being present- 

 About natural size. 



Fig. 2a. Anterior view of the same shell, showing gibbosity 

 and arcuity of shell, as well as concentric lines of growth. About 

 natural size. 



Figs, ab and 2c. Anterior and lateral views of the left valve of 

 a young individual of the above shell. About natural size. 



Fig. 3. Pseiidomonotis Jiawni cqiiistriala. Left valve of type. A 

 little less than natural size. 



Figs. 3a and 3b. Anterior views of two left valves showing 

 variation in convexity and indistinctness of beak. About natural 

 size. 



