A. E. Verrill — Catalogue of Marine Mollusca. 
541 
without a fold ; operculum paucispiral. Animal, with frontal ten- 
tacles united by a fold, and with simple posterior tentacles. Head 
thick and short, with large retractile pharynx. Jaws well developed. 
Radula with three rows of rhachidian teeth ; broad, bilobed, inner 
lateral teeth; and two rows of small, hook-shaped, outer lateral ones. 
Gill large, attached to the inner surface of the mantle on the left 
side of the neck, and extending over to the right side, consisting of 
numerous lamellae. 
Choristes elegans Carp., variety tenera Y. 
Choristes elegans Carpenter, Canadian Nat., vi, p. 392, pi. 7, fig. 13, 1872. 
Plate LYIII, figures 27, 2 7 as. 
Shell thin, fragile, heliciform, with a low spire and a very large, 
ventricose 'body-whorl. Whorls, in our largest examples, four to 
five, very convex and evenly rounded; apical whorl small, spiral, 
obliquely upturned and incurved, but not prominent; suture deeply 
impressed ; surface smooth. (The epidermis is mostly destroyed 
and the surface of the shell eroded in all our living specimens.) The 
whorls are largely in contact and united well together, though the 
periostraca is continuous between them. Aperture large, forming 
more than a half-circle ; the outer side is well rounded, the columella- 
margin nearly straight ; lip sharp, continuous all around, raised up 
and with the edge slightly everted in the umbilical region, so as to 
partially conceal the umbilicus, which is rather large and deep, nearly 
circular within. Operculum thin, horny, pale yellow, round-ovate, 
spiral, with two to three rapidly enlarging whorls, the nucleus ex- 
centric. 
The animals of several alcoholic specimens were examined. Head 
large, short, thick, rounded or truncate, with two short, flat, obtuse, 
anterior tentacles, wide apart, but connected together by a transverse 
fold; posterior tentacles, short, thick, conical, smooth; no eyes visi- 
ble; proboscis short, thick, retractile ; jaws crescent-shaped, strong, 
black. Verge situated just below the right posterior tentacle, small, 
papilliform, swollen at base; below this and farther back, a larger 
and thicker papilla with basal swelling; on each side, between the 
mantle and foot, at about midlength of the foot, a small mammiform 
papilla ; and two small flat cirri, behind and beneath the operculum. 
Foot broad, ovate, with two tentacle-like processes in front. Gill 
large, consisting of numerous thin lamellae, attached to the inner sur- 
