CONCHIFERA. 



HoRisTisiA, Laube, 1865. 



Dedicated to Director Dr. Moriz Homes. 



Type, Geryillia socialis, Sckloth, St. Cassian. 



Differs from, the typical Gervillise by the peculiar structure of 

 the hinge, and by a more or less lengthened septum going 

 through the cavity of the umbones. The genus is intermediate 

 between Cassianella and GerviUia. 



Nataddta, Munier-Chalmas, 1863. 



Type, N. Heberti, Munier, Cenonamian, Aubeterre. 

 Shell resembling a transverse Vulsella, rostrated posteriorly ; 

 the internal fibrous layer is wanting. 



Eligmtjs, E. Deslongchamps, 1856. 



Etymology, eAtyftos, a sinuosity, in allusion to the sinuosities 

 of the borders of the post-apical opening. 

 Type, E, polytj^us, E. Deslong. Eig. 27 



Fig. 27. — Eligmus Polytypiw. 



Animal unknown. 



Shell free, or perhaps attached by a byssus, nearly equi- 

 Talve, inequilateral; ovate or cylindrical, more or less com- 

 pressed ; anterior extremity inflated, and shorter than the 

 attenuated posterior one. Test rather thick, foliaceous. Um- 

 bones inflated, slightly depressed or flattened, diverging and 

 directed backwards. Valves closed at both extremities, with 

 an unsymmetrical (byssal?) sinus, s, behind the umbones; 

 ornamented by oblique, radiating carinated ribs. Hinge 

 short, straight, edentulous ; ligamental area triangular, with a 

 superficial pit, L Muscular scar single, situated on the free 



67 



