RETUSA. 217 



Northwest Atlantic and West Indian species. 



R. GOULDII Couthouy. 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, o 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. ( Old.*). 



Alt. 7i, diam. 3f 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. (Binuey edit.) p. 217, f. 508. Utriculus (Retusa) 

 gouldii DALL, Cat. Moll. S.-E. U. S., p. 86. Cylichna gouldii VER- 

 RILL, Amer. Journ. Sci. (3), xx, p. 399. Aplustrum gouldii SOWB., 

 Conch. Icon., f. 1. 



R. PERPLICATA Dall. Unfigured. 



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 



