ONUSTID^. 215 



Spiricella, Bang. 

 Distr. — S. iinguiculus,'Ra,ng (Ixv, 96, 91). Miocene; France. 

 Shell flattened, elongated, with a small sinistrally spiral apex. 

 Perhaps as nearly related to Umbrella. 



Amathina, Gray. 



Distr. — A. tricarinata (Ixv, 98, 99). India. 



Shell depressed, oblong ; apex posterior, not spiral, with three 

 strong ribs radiating from it to the anterior margin, which is 

 prodnced 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, Morch. 



Distr. — 10 sp. W. Indies, W. America, Indian Ocean, Philip- 

 pines, Australia. Fossil, 10 sp. Cretaceous ; United States, 

 Europe. H. cornucopise, Lam. (Ixv, 100, 1, 2). 



Shell thick, obliquely conical, non-spiral, apex somewhat pos- 

 terior and curved backwards ; muscular impression horseshoe- 

 shaped ; base of attachment shell}^, 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., 181*7. (Sabia, Graj^) 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 Turbinellse of the 

 Eastern seas. H. conica, Schum. (Ixv, 3, 4). 



Family ONUSTID^. 



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 



