BULLID^. 359 



narrow behind, widened in front ; columella with two folds. G. 

 bidentatus, d'Orb. (Isxxvii, 33). Tertiary ; West Indies. 



VOLVULA, A. Adams. Shell subeylindrical, attenuated to a 

 point posteriorly^, to which the narrow aperture extends ; spire 

 concealed ; outer lip sharp ; columella with an obsolete anterior 

 plication. G. acuminata^ Brug. (Ixxxvii, 34). 



AOT^ONELLA, d'Orb. (Volvulina; Stolicz.) Shell convolute, 

 like Yolvula, attenuated at both ends, aperture linear, inner lip 

 anteriorl}^ thickened and provided with three folds. The shells, 

 which are as yet only known from cretaceous deposits, mostlj' 

 closel}^ resemble the recent Volvula, differing from it merely by 

 the presence of three columellar folds on the anterior portion of 

 the inner lip. C. crassa^ d'Orb, (Ixxxviii, 61). Cretaceous. 



Utriculus, Brown. 



Distr. — Northern. Several sp. U. Gecillei, Phil. (Ixxxvii, 32). 



Shell subeylindrical, with short spire, and thin epidermis; 

 aperture narrow behind, wider in front ; columella not plicated; 

 outer lip thin. 



Utriculus is regarded as a distinct genus by Jeffreys, differing 

 from Cylichna by the tentacles being separate, the eyes distinct, 

 the gizzard horn^^, and the shell having a visible spire with a 

 mammillary apex, 



DiAPHANA, Brown. 



Syn. — Amphisphyra, Loven. 



Distr. — A few sp. Northern, U, S., Europe. D. debilis, Gould 

 (Ixxxvii, 35), 



Shell thin, transparent, oval-globular; spire very short; aper- 

 ture much widened anteriorly ; columella a little sinuous ; outer 

 lip thin, sinuous, broadly rounded anteriorly. 



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

 lateral, wide apart ; eyes immersed in their hind bases. Mantle- 

 margin slightly thickened. Foot short, bilobed behind. 



In this genus, as in Rissoella, Gra}^, the eyes are placed far 

 back behind the head, so that in order to render the vision of 

 the animal distinct, the shell is nearly transparent. The head of 

 the animal is very short, and the tentacles wide and far apart. 



Family BULLID^, 



Shell spiral, ventricose, rather thick ; maculated and banded 

 in the typical genus, white in others; spire involute; external, 

 but usually partly covered by the lateral lobes of the foot. 



Bulla, Linn, 

 Distr. — 50 sp. Universal. B. ampulla, Linn. (Ixxxvii, 36), 

 Fossil. Cretaceous — . 



Shell oval-globular, smooth, spotted, marbled or zoned ; spire 



