170 Trans. Acad. Sci. of St. Louis. 



teeth, but less distinct than those of the posterior. Anterior 

 muscular scar subcircular, situated near the upper anterior 

 angle. Posterior scar larger than the anterior, with its upper 

 margin excavated out of the hinge plate. Pallial line entire, 

 connecting- the muscular scars." 



"Surface smooth, except a few concentric undulations, 

 which are scarcely visible except on the upper side of the pos- 

 terior umbonal slope." 



Dimensions of one of the type specimens: length 11 mm., 

 height 7 mm., convexity of one valve 2 mm. 



Remarks. This is a common species of the fauna. The 

 concentric markings of the shell are perhaps a little more 

 strongly marked than the original description indicates, and 

 the muscular impressions are always faint and are usually not 

 recognizable at all. The basal margin is often straight with 

 no indication of a slight emargination. 



Edmondia nuptialis Win. 



PI. XV. f. 13. 



Original description. " Shell of moderate size, trans- 

 versely-suboval ; in adult specimens considerably inflated in 

 the vicinity of the pallial border. Beaks subcentral, small, 

 incurved, somewhat elevated above the moderately extended, 

 slightly arcuate hinge-line. Ventral margin gently curved 

 or nearly straight in the middle, more rapidly curved to- 

 ward the rounded, subequal extremities. Hinge structure 

 obscure, but apparently consisting of one or more lateral 

 teeth on each side of the beak. Surface unequally and inter- 

 ruptedly furrowed. Greatest thickness through the middle of 

 the shell." 



The dimensions of the type specimen are: length 20 mm., 

 height 16 mm., and convexity of one valve 6 mm. 



Edmondia strigillata Win. 



PI. XV f. 12. 



Original description. " Shell rather smaD, rather gibbous, 

 transversely oval ; beaks subcentral, elevated, obtuse, some- 

 what strongly turned forward. Ventral margin gently arcuate 

 in the middle, more rapidly curved toward the neatly rounded 

 extremities, of which the posterior is broadest. Hinge-line 



