362 PURPURID^. 



variety is Lamarck's species P. imbricata. (See De Kay, 1. c. pi. 

 viii. fig. 172.) 



As to coloration, both varieties pass from white through yellow 

 to a dark chocolate or slate-color ; but specimens of the first group 

 are both lighter and darker than those of the second group. It is 

 in the first group only that I have met with the banded varieties. 

 These have the portion next the suture, the base, and a central zone 

 dark, and the remainder white ; and they constitute Lamarck's spe- 

 cies bizonalis (v. De Kay, 136, pi. viii. fig. 174)i. Kiener has fig- 

 ured many varieties, but it would be impossible to represent every 

 aspect of a shell, in which no two individuals may be found exactly 

 alike. 



Kiener states that the animal, which is ])erfcctly white, is very 

 carnivorous, and that by it arc produced, principally, the perfora- 

 tions so frequently observed in bivalve shells on the shore. This 

 remark might apply to many of the perforated univalve shells ; but 

 it would hardly be expected that this animal, whose residence is 

 confined to the rocks, should feed upon the animals of bivalve shells, 

 which reside only in sand or mud. The NaticidcB are the more 

 probable depredators in this case. 



Genus IV ASS A, Lamarck. 1799. 



Shell ovate, ventricose, body whorl variously sculptured ; aper- 

 ture ovate, with a short, reflected, truncated anterior canal ; inner 

 lip smooth, often widely spread over with enamel, with a posterior 

 callosity or blunt dentiform plait; outer lip dentated, internally 

 crenulated. 



Nassa obsoleta. 



Fig. 210. 



Shell ovate, dark reddish-brown, covered with a network of lines, and often- 

 times folded; aperture ovate, dark violet, right lip simple and sharp, with ele- 

 vated lines within. 



jYrtssrt obaohin. Say, Jonrn Acad. Nat. Sc. ii. 232. — Stimpson, Check Lists, 5. 

 Bnccinum Nov-Ehoracensis, Wood, Index, Suppl. pi. 4, fig. 26. 



Bnrcinnm oliciforme, Kiener, Iconog. {Buccin), pi. 2.5, fig. 99. — Lam. An. sans Vert. x. 201. 

 Burcinmn obsoktnm, AvxMS, Bost. Journ. Nat. Hist. ii. 2G7.— Gould, Inv. Isted. 308, 

 fig. 210. 



Shell ovular, inelegant, dark reddish-brown or olive colored, 

 somewhat shining; whorls six, convex, composing a moderately 



