362 LOPHOCERCID^. 



BULLOPSis, Conr. Like Hydatina with a depressed spire and 

 inflated body-whorl, inner lip with two close folds. B. cretacea^ 

 Conr. Cretaceous ; Mississippi. 



Etallonia, Deshayes, 1864. 



Etym. — Dedicated to M. Etallon, a French palseontologist. 



Distr. — 3 sp. Eocene ; Paris basin, Valognes. U. prisca, 

 Desh. (Ixxxviii, 62). 



Shell ovate, subfusiform, resembling certain small Mitres ; 

 spire short, conical, obtuse, few-whor!ed ; aperture elongated, 

 narrow, base entire, subemarginate ; lip simple, acute, arched ; 

 columella thick, cylindrical, twisted in the middle to resemble 

 an obtuse plait ; acute anteriorly. 



Family LOPHOCERCID^. 



Shell spiral, very thin, subflexible, with epidermis. 



Head with two ear-like tentacles ; eyes sessile on the sides of 

 the head ; gill regular, pectinate : organs of generation close 

 together in one tubercle ; male organ on the right side of the 

 nape near the tentacle. In Lophocercus, the body is covered 

 with papillae, and produced behind into a long, pointed tail ; foot 

 with the natatory appendages undivided, reflexed and partly 

 covering the shell in front and united posteriorly. 



Lophocercus, Krohn. 



Syn. — Icarus, Forbes. Oxynoe, Eaf. 



Example. — L. Sieboldi, Krohn (Ixxxix, 68, Y0\ 



Shell like Bullsea ; convoluted, thin, ovate, covered with epi- 

 dermis, outer lip separated at the suture, posterior angle inflected 

 and rounded. 



Animal slender, papillose ; tentacles 2, ear-shaped ; eyes sessile 

 on sides of head ; side-lobes reflected and partly covering the 

 shell, united behind ; tail long and pointed. 



voLVATELLA, Pcase. Shell resembling Lophocercus, but more 

 convolute. Foot small, mantle concealed, vent posterior, eyes 

 concealed in the fold of the sides of the head. L fragilis^ 

 Pease. 



Akera, Miiller. 



Etym. — Akeros, hornless. 



Distr. — 7 sp. Greenland, Great Britain, Mediterranean, East 

 Indies, New Zealand. A. soluta, Chemn. (Ixxxix, 63). Fossil. 

 Eocene. 



Shell thin, flexible, globosely cylindrical, spire truncated, 

 whorls channeled ; aperture long, expanded and deeply sinuated 

 in front, outer margin disunited at the suture; columella open, 

 exposing the whorls. 



Head-disk greatly elongated, wide and bifld anteriorly, and 



