OF CONCHOLOGY. 81 



The conoidal form, referred to in Thes. Con., from Borneo, 

 is probably also distinct. I received from the late Dr. Gould a 

 specimen of that shape, collected in the Sooloo Seas, resembling 

 cethiojjis, Mke. 



Separating the planulate and conoidal forms from T. pei'specti, 

 kc, in Thes. Con., the three species remaining may be distin- 

 guished by the following characters : — 



The West Coast species is the largest, most elevated and 

 whorls generally more convex, and rounded at periphery of last 

 whorl. The East Indian form is the nearest allied to it in those 

 characters, while the Hawaiian species is depressed and the 

 whorls generally more flat. 



The sculpture of the West Coast species agrees more nearly 

 with the Hawaiian. The concentric ribs being flat or planely 

 convex, the intervening groove being light and the radiating 

 striae finer and more continuous ; while the sculpture of the East 

 Indian form is more coarse and bold, the concentric ribs rounded 

 and more distinct, the grooves intervening being much deeper. 



In color the West Coast and Hawaiian are more plain, the 

 former more brown, the latter darker, and more or less spotted 

 with white at the suture and on the periphery of last whorl, and 

 encircled with white at margin of the umbilicus. The East 

 Indian is variegated with white and black, either tessellated or 

 disposed in radiating lines, and generally a white band following 

 the suture. 



The operculum of the Hawaiian and East Indian agree, and is 

 well figured in Adams' "Genera." That of the West Coast 

 species difi"ers widely. It is composed of plates disposed in the 

 shape of a screw, of three whorls. The plates are wide apart, 

 and furnished on their edges with short, stout bristles, and the 

 sides coarsely reticulated with raised striae. (Plate viii, fig. 6.) 



The animal of the East Indian species is fairly represented in 

 Voy. d' Astrolabe, and agrees with my observations, except that 

 the emargination in front is too angular. The dilatation of the 

 anterior corners of the foot is common to all the species I have 

 examined. The animal of the Hawaiian species differs from the 

 above in the tentacles being longer and more slender, " the foot 

 widest posteriorly," and color pale cinereous. I may as well 

 note here that the animal of T. 3IigJielsii, Phil., agrees with the 

 above in general shape. Its tentacles are, however, setaceous, 

 and color pale cream. Both species inhabiting the Hawaiian 

 Islands are found almost invariably on branched coral, and 

 suspend themselves by strong gelatinous threads, one of which 

 will sustain the weight of several shells and can be drawn out 

 four or five inches. 



