104 AMERICAN MARINE CONCIIOLOGY. 



grooved ; outer lip arching forward ; inner lip with a thin coat of 

 enamel, with a single oblique fold or small tooth near the base ; 

 whitish, immaculate. 



Length 2.5 to 5 mill. 



New England; South Carolina. 



3. U. biplicatus, H. C. Lea. Fig. 213. 



(Bulla.) Proc. Bost. Soc. Nat. Hist,, 204. 1844. 

 Shell cylindrical, subquadrate, thick, whitish, polished, ivory- 

 like ; spire concealed ; last whorl with a callus above, and small 

 transverse striae below; mouth narrow above, ovate below ; colu- 

 mella with a large and a small fold. 



Cape May, N. J. 



Genus DIAPHANA, Brown. 

 Conch. Text-Book, 112. 1833. 



Head-disk broad and short; tentacular lobes short, conical, 

 lateral, wide apart; eyes immersed in their bases behind; mantle- 

 margin slightly thickened; foot short, bilobed behind. 



There are but few species, of northern distribution. 



1. D. iitemalis, Couth oivy. Fig. 214. 



(Bulla.) Bost. Journ. Nat. Hist., ii. 180, t. 4, f. 5. 1839. 

 llriculus globosus, Loven, Ind. Moll. Scand. 1846. 



Shell globular, very thin and brittle ; the bocty-whorl envelop- 

 ing all the others so as to leave no perceptible spire, and marked 

 with the lines of growth ; aperture narrow above, dilated be- 

 neath ; outer lip strong, and regularly curved ; it revolves from 

 its junction behind nearly a third of a revolution before it turns 

 forward; columella slightly arcuated and reflected upon the .body 

 of the shell so as to form a small but distinct umbilicus ; hyaline, 

 with brownish tinge. 



Length 2.5. mill. 



New England, northwards. (Eur.) 



2. D. hyaltnus. Turton. Fig. 215. 



{Utrirulus.) Loudon's Mag. Nat. Hist., vii. 353. 1833. 

 Bulla debilis, Gould, Am. Journ. Sci., xxxviii. 196. 1840. 



Shell small, obliquely ovate, tumid, thin and brittle ; wdiorls 

 four, all rising to the same height, convexly rounded ; last whorl 

 the whole length of the shell ; surface smooth ; aperture as long 

 as the shell, widening below, outer lip slightly waved, inner lip 



