1 SYNOPSIS OF GENERA. 



The species of this genus apparently constitute a very natural group, since 

 they present such characteristic features of form and surface characters. 



These shells have sometimes been referred to Modiomorpha and to Sanguinolites, 

 but they are clearly distinct from either, and cannot be properly referred to any 

 previously established genus. 



Some of the species in their natural condition have had considerable con- 

 vexity, or even gibbosity, in the umbonal region ; but they are evidently thin 

 shells, and usually much compressed. The shell rarely preserves evidence of 

 radiating striaa, which are scarcely superficial. 



Examples: Glossites teretts, pi. xcvi, fig. 15. 



Qlossites lingualis, pi. xl, figs. 16, 17 ; pi. xcvi, figs. 9-11. 

 Glossites elliptictis, pi. xcvi, fig. 8, 



Elymella, n. gen. [Type, Elymella nuculoides. Hall.] 



Shell equivalve, inequilateral, ovate-elliptical. Anterior end very short and 

 the margin rounded. Posterior end narrower and rounded at the extremity. 

 Beaks closely incurved; umbo prominent. Cardinal line short. Umbonal 

 slope prominent in the upper part, not defined and merging into the general 

 convexity of the shell. 



Surface marked by fine concentric striae of growth, which are sometimes 

 lamellose and elevated into concentric ridges. 



Hinge-line short, the internal characters undetermined. Muscular impres- 

 sions unknown. 



The small group of shells here termed Elymella cannot, with propriety, be 

 referred to any established genus, and therefore this name has been chosen in 

 reference to the form and expression of the fossils. The form of the shell and 

 the direction and character of the concentric striae resemble some species of 

 Nucula ; but although occurring with specimens of the latter genus showing the 

 hinge teeth, none of the specimens of Elymella have preserved any indication of 

 such characters. 



Examples: Elymella fabalh, pi. xl, figs. 5, 9. 



Elymella nuculoides, pi. xl, fig^. 6, 7, 8. 



