CONCHIFEEA. 



HoRiSTESiA, Laube, 1865. 



Dedicated to Director Dr. Moriz Homes. 



Type, Gervillia socialis, Sckloth., St. Cassian. 



Differs from the typical Gervillise by the peculiar structure of 

 the binge, and by a more or less lengtbened septum going 

 tbrougb the cavity of the umbones. The genus is intermediate 

 between Cassianella and Gervillia. 



Natadi^-a, Munier-Chalmas, 1863. 



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

 Shell resembling a transverse Vulsella, rostrated posteriorly ; 

 the internal fibrous layer is wanting. 



Eligmus, E. Deslongcbamps, 1856. 



Etymology, eXty/xos, a sinuosity, in allusion to tbe sinuosities 

 of tbe borders of the post-apical opening. 

 Type, E. polytypus, E. Deslong. Eig. 27 



Fig. 27. — Eligmus Polytypus. 



Animal unknown. 



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

 valve, 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. Yalves 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, I. Muscular scar single, situated on the free 



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