DFAPHANA. 281 



second section of that genus. Utricuhis is, however, a mere syno- 

 nym for Retnsa, which Browu proposed as a substitute for his own 

 earlier name. 



The genus differs from Retusn in possessing a radula, in the ab- 

 sence of stomach plates, etc. The shell is more globose and fragile 

 than in Eetusa or Ci/lichna, with a larger umbilicus, thin columella 

 and without distinct sculpture. The lack of epipodial lobes and of 

 uncini also distinguishes this genus. 



D. DEBiLis Gould. PI. 59, fig. 27. 



Shell thin, fragile and somewhat transparent, light brownish 

 corneous, irregularly ovate, broadly globose below, narrow and sub- 

 angular above. Apex large, globose, obliquely and mamillarly pro- 

 jecting ; subsequent whorls 2], the inner very narrow; convex, 

 planorboid, separated by deep sutures, the latter part of the last 

 whorl somewhat descending. Body-whorl compressed above, swollen 

 below, very lightly sculptured with indistinct growth-lines. Aper- 

 ture nearly as long as the shell, narrow and biangular above, broadly 

 rounded below; outer lip thin and sinuous: columella long and 

 nearly straight, not thickened, the edge somewhat reflexed above, 

 partly closing the narrow umbilicus. 



Alt. ^l diam. 2^ mill. 



Greenland to Connecticut. 



Bulla clebilis Gld., Amer. Journ. Science xxxviii, p. 196 (1840); 

 Otia Conch., p. 179 ; Invert. Mass., p. 164, f. 951.— DeKay, N. Y. 

 Moll. p. 17, pi. 35, f. S2d.— Bulla (Aplnstrum) debile Ad., Thes. 

 Conch., p. 564, pi. 120, f. 8. — Aplustrum debile Sowb., Conch. Icon, 

 f. 3. — Diaphana debilis Stimpson Check-Lists, p. 4 ; — W. G. Binn. 

 in Invert. Mass., p. 216, f. 507. — Leche, Kongl. Svensk. Vet.-Akad. 

 Handlingar, 1878, p. 71. — Akera subangulata Moller, Ind. Moll. 

 Groenl., p. 6. Sowb., C. Icon, xvi, f. 1. 



I have retained this species separate from D. hyalina because in 

 the specimens before me the apex projects as in D. seguenzce, which 

 does not seem to be the case with Scandinavian specimens of 

 hyalina. 



D. I.OTT.E Bush. PI. 59, figs. 32, 33. 



Shell rather large, short and stout, abruptly tapered at the ends, 

 truncate at the top with the two whorls of the spire showing in a 

 shallow pit ; translucent, yellowish-white, with a slightly lustrous 



