23-4 BULLETIN OF THE 



Family AMPHIPEKASID^. 

 Genus AMPHIPERAS Gronovius. 

 Subgenus SIMNIA Risso. 

 Simnia Risso (Leach MS.), Hist. Nat., IV. p. 235, 1826. 



This genus was not proposed on the character of a sharp outer lip, as stated 

 by Tryon and others. In fact Risso's figure of his type species shows the 

 smooth narrow thickening of the lip exactly as it occurs. It was rather the 

 general form of the shell, elongate and without the thick and dentate peritreme 

 characteristic of Ovula carnea Risso and related species. 



In a valuable paper in the American Journal of Conchology (VI. p. 183) 

 Prof. Theodore Gill has treated of the relations of Amphiperasidce. Here he 

 characterizes the group as having a shell simply rolled upon itself and thus not 

 spiral ; and in this respect he associates with them the genus Pedicularia. Now 

 I have already shown, and elsewhere figured in this paper, the young spiral 

 shell of Pedicularia, and a happy accident has enabled me to discover that the 

 young (not embryonic) shell of Si?nnia (Neosimnia) uniplicata Sby. is also 

 spiral, and so continues for some four whorls before putting on the involved 

 roll of the adult. Of course Prof. Gill's merit in discriminating the distinction 

 between the enrolment of the adult Amphiperas and Cypr&a, which had been 

 overlooked by conchologists, is not affected by this discovery, and he expressly 

 excluded the embryonic shells from his generalization, as they were at that 

 time unknown. 



I suspect that the type, of Radius Montfort will be found to differ from the 

 Simnia group, otherwise the name Radius has priority. Neosimnia Fischer 

 forms a convenient section of Simnia, but the distinction between the two is 

 very slight in some species, and it sometimes happens that one might easily 

 assign the same species to one or the other according to the stage of growth 

 which it has attained. 



There is no reason to think that the genus Rhizorus Montfort has anything 

 to do with Simnia, as claimed by Mbrch. 



Simnia acicularis Lamarck. 



Ovma acicularis Lam., Ann. du Mus., XVI. p. 112, No. 9; Anim. s. Vert, VII. 



p. 369, 1822; ed. Desh., X. p. 472. 

 Ovulum aciculare Sowerby, Thes. Conch. Ovulum, No. 31, p. 477, pi. c. figs. 43-46, 



1848; Reeve, Conch. Icon. Ovulum, pi. xii. figs. 53 a, 53 b, May, 1865. 



Habitat. Brazil and South Carolina, Sby. Florida, Hemphill. North and 

 South Carolina, Kurtz & Stimpson. Sigsbee, off Havana, in 80 fms., and 

 off Sombrero, in 70 fms. Twenty-five miles off Cape Fear, North Carolina, 

 U. S. Fish Commission, at Station 2619, in 15 fms., sand. 



