RETUSA. 217 



Nortlnvest Atlantic and Wed Indian species. 



K. GOULDii Couthou>. PL 23, figs. 58, 59. 



Shell small, ovate, shining, of a dead white color, covered with a 

 yellowish epidermis; whorls four, rounded at their upper edges, 

 their dividing line well marked ; the last whorl is as long as the 

 shell, and includes all the others; under the magnifier its surface 

 appears covered with revolving lines ; the whorls all rise to about 

 the same level, so that the summit is nearly flat ; the anterior extrem- 

 ity is rather narrower than the posterior ; the aperture is narrow 

 behind, and suddenly enlarged by the curvature of the inner mar- 

 gin, which is a little thickened, white, and polished. The outer lip, 

 from its junction behind, advances a little as it turns forward by a 

 regular curve, and finally turning backward by a rather sharp 

 turn, it joins the body of the shell with a gentle twist; umbilicus 

 none. (Gld.). 



Alt. 71, diam. 3 J mill. 



Maine to Hatteras. 



Bulla gouldii Couth., Bost. Journ. Nat. Hist, ii, p. 181, pi. 4, f. 

 6, 1839.— Gould, Inv. Mass., p. 163, f 94— DeKay, N. Y. Moll, 

 p. 15, pi. 5, f 101. — Utriculus gouldii Stimp., Check-lists, p. 4. — 

 Gould, Inv. Mass. (Binney edit.) p. 217, f. 508. — Utriculus (Retiisa) 

 gouldii Dall, Cat. Moll. S.-E. U. S., p. 86. — Cylichna gouldii Ver- 

 RiLL, Amer. Journ. Sci, (3), xx, p. 399. — Aplustmm gouldii Sowb., 

 Conch. Icon., f. 1. 



R. PERPLICATA Dall. CJnfigured. 



Shell ivory white with a very thin translucent epidermis, marked 

 only with delicate lines of growth and a few faint incised spirals 

 near the columella; anterior half of the shell wide and rounded, 

 posterior half narrowing toward the apex with the sides somewhat 

 compressed or flattened; outer lip thin, straight except in front 

 where it expands a little before rounding to the rather thick twisted 

 pillar ; behind deeply notched and behind the notch arching over 

 and turning forward to meet a carina which revolves about the 

 apex ; apex truncate, carinated by a line which forms the outer 

 boundary of the path of the notch ; within vorticiform, about one and 

 a half whorls visible around the central perforation and descending 

 into it ; body with hardly any wash of callus ; pillar strong, with a 

 large horizontal fold and a minute chink behind it ; aperture as long 



