194 



the number, position, or absence of teeth, according to which the 

 genera arc now founded, are so gradual as to compel us to regard 

 them as merely sub-genera of one grand genus. [More recent exami- 

 nations of the structure of the mollusks conclusively show that the 

 natural divisions among the Naiads are numerous.] Should this view 

 be adopted, and to it l>r. (1. is much inclined, he believes that another 

 sub-generic group might be instituted, equally as characteristic as any 

 now received; and proposes as follows : — 



Subgenus PsETJDODON. Hinge margin with a tooth-like apophysis 

 on each valve, the surface of which is not fractured, but smoothly 

 covered with enamel, fitting into corresponding undulations in the 

 opposite valve, that on the right valve closing in front of that on the 

 left. 



Anod. inoscularis would be the type of this group, and to it would 

 belong A. Salweniana, edentula, Stewartii, and perhaps some others. 

 [Perhaps equivalent to Monocondylcea, D'Orb.] 



Helix setigera [iiystrix]. T. discoidea, parva, tenuis, fusco et 

 luteo tessellata ; supra planulata, apice indentata; anfractibus quinis, 

 clathris creberrimis setigeris aliquando denudatis insignibus; subtus 

 late umbilicata ; apertura lunata, lamellis duabus intends conspicuis 



volventilms. 



[Diam. 1 ; axis, J ff poll. Hab. East Maui, Sandwich Islands- 

 Like H. dcedalea and H. contorta in form and coloration, but larger 

 than either, and further distinguished by the fewer lamellae and the 

 long coarse hairs which it bears. The name first given was preoccu- 

 pied, and one suggested by Dr. Mighels is substituted.] 



Helix Stellula. T. parva, discoidea, supra planulata, subtus 

 convexa, utroque umbilicata, fusca interdum luteo maculata ; anfrac- 

 tibus quatuor triquetris, costibus frequentibus elevatis, acutis, ad peri- 

 pheriam carinatam stellatis: apertura rhomboidca, lamella unica 

 interna, clevata, volvcnte instructa ; labro simplici. 



[Diam. 1 ; axis, X V poll. Hab. Maui, Sandwich Islands. Distin- 

 guished by its angular whorls and very prominent ridges, which pro- 

 ject at the periphery so as to resemble the rowel of a spur.] 



Vol. ii. 26, (January, 1845.) 



Aciiatina apusta. T. turrita, imperforata, solida, fusco-nigricans 

 sursum pallescens ; apice pyramidata ; ani'r. 7 convexis, leviter stria- 

 tis, ultimo subcarinato : apertura ovalis, intus opalina ; labro simplici, 

 acuto, nigro ; columella eburnea, antice in dentem product;!. Lwig. 

 \i ; lat. \ poll. Hab. Kauai, Sandwich Islands. 



This shell partakes of the characters of both Achalina and Acliati- 

 nella [subgen. Carelia H. and A. Adams]. Occasionally, instead of 



