108 Description of Eight new Species of Shells. 



Shell transverse, obovate, smooth, polished, greenish, diapha- 

 nous, marked with purple lines ; valves thin ; beaks somewhat 

 prominent, sub-acute. 



Length -08. Breadth -15. Diam. -05 of an inch. 



Var. ct. Minore, compressiore, castaneo-brunnea, sine lineis 

 purpureis. 



Smaller, more compressed, chestnut-brown, without purple lines. 



Hab. Delaware Bay. Cabinet of I. Lea. 



Remarks. — This species varies very much, both in form and 

 color. The var. a may perhaps prove a species. The markings, 

 as in the preceding species, are frequently zigzag. There are 

 transverse lines of growth, only visible with a powerful micro- 

 scope. In form it somewhat resembles the Modiola tulipa. It 

 might be confounded with the very young of Mytilis edulis, but 

 the difference in color and shape, as well as in the position of the 

 beaks, will distinguish it on a very slight examination. 

 Genus Crepidula. — Lamarck. 

 C. acuta. PI. 1, fig. 4. 



C. testa ovata, valde convexa, sub-tenui, tevi, externe fusca, 

 intus tenebroso-castanea ; epidermide luteo-fusca ; apice acuto, 

 recto ; cyatho sub-triangulari, albido, diaphano, sub-convexo, 

 vix a?quaU trienti testes longitudinis ; apertura elliptica. 



Shell ovate, very convex, somewhat thin, smooth, externally 

 brown, internally dark chestnut ; epidermis yellowish brown ; 

 apex acute, straight ; cyathus sub-triangular, whitish, diaphanous, 

 somewhat convex, scarcely equal to a third the length of the 

 shell ; mouth elliptical. 



Length -17. Breadth -1. Height -05. Length of cyathus 

 •05 of an inch. 



Hab. Delaware Bay. Cabinet of I. Lea. 



Remarks. — This little species of Crepidula belongs to the C7^e- 

 pipatella, Lesson, a sub-genus of Calyptrcea. The color inter- 

 nally varies from a chestnut brown to a horn color with brown 

 marks. The cyathus or diaphragm, in common with our other 

 species, is convex, the convexity usually ending at a regular line, 

 about one fifth from one side, beyond which it is flat ; it also gen- 

 erally comes a little further down on one side than on the other. 

 It is usually very regular in its form. It bears a slight resem- 

 blance to the Crepidula glaiica, but that shell is flatter when 

 young than when old ; besides which, the acute apex, less width, 

 and want of transverse lines, will immediately distinguish it. It 



