qa 
ONUSTIDA. 21 
SPIRICELLA, Rang. 
Distr.—S. unguiculus, Rang (lxv, 96, 97). Miocene; France. 
Shell flattened, elongated, with a small sinistrally spiral apex. 
Perhaps as nearly related to Umbrella. 
AMATHINA, Gray. 
Distr.—A. tricarinata (\xv, 98,99). India. 
Shell depressed, oblong ; apex posterior, not spiral, with three 
strong ribs radiating from it to the anterior margin, which is 
produced into three points. 
Head elongated; eyes sessile on the posterior lateral margins 
behind the tentacles; tentacles short, obtuse; mantle-margin 
entire, a tentacular median filament at the hind-part. 
Hipponyx, Defrance. 
Etym.—Hippos, a horse, and onyx, a hoof. 
Syn.—Cochlolepas, Klein. Krebsia, Mirch. 
Distr.—10 sp. W. Indies, W. America, Indian Ocean, Philip- 
pines, Australia. Fossil, 10 sp. Cretaceous; United States, 
Europe. H. cornucopizx, Lam. (1xv, 100, 1, 2). 
Shell thick, obliquely conical, non-spiral, apex somewhat pos- 
terior and curved backwards; muscular impression horseshoe- 
shaped; base of attachment shelly, secreted by the foot of the 
animal, 
Animal oval or suborbicular, conical or depressed ; foot very 
thin, a little thickened towards the margins; head globose, 
separated from the body by a neck-like constriction ; eyes upon 
swellings of the tentacles. 
AMALTHEA, Schum., 1817. (Sabia, Gray.) Like Hipponyx, 
but forming no shelly base; surface of attachment worn and 
marked with a crescent-shaped impression. Often occurs on 
living shells, such as the large Turbos and Turbinellie of the 
Eastern seas. HH. conica, Schum. (1xv, 3, 4). 
Famity ONUSTID i. 
Shell conical, spiral, depressed, umbilicated, soldering shells 
and stones to its exterior surface. 
Animal. Foot small, cylindrical, used for jumping, not walking, 
having an expanded front, and a tapering hind-portion. Oper- 
culum large, horny, subannular , right half free, nucleus lateral, 
dextral; muscular impression sinistral, semilunar, extending the 
whole length. 
These animals scramble along like the Strombs; they extend 
and fix the front, dilated part of the foot and draw the hind-lobe 
up to it, throwing forwards the shell at every movement. They 
cannot ‘glide like other. mollusks, but the form of the foot is 
