CHARACTERISTIC DEEP-SEA TYPES. — GASTEROPODS. 69 
the case of the former to the application of several specific names. 
The depth in which these have been found 
varies from 125 to over 1,000 fathoms. 
Pleurotomaria is one of the most remark- 
able forms dredged in the continental region. 
Four recent species of the genus are known. 
Its history dates back to the earliest fossilifer- 
ous rocks of the cambrian, and to the dredg- 
ings of the * Hassler” and the “ Blake” are 
due the only knowledge yet acquired of its 
soft parts. ‘Two species are found in the 
West Indies, of which the 
finest is P. Adansoniana 
(Fig. 288), from about 200 
fathoms. The shell is four 
inches in diameter, richly 
pearly within, and orna- 
mented with elegant red 
and brown colors exter- 
nally. The anal notch in 
this species extends nearly 
half the length of the last 
whorl. A second species, 
less brilliant and with a 
Fig. 288. — Pleurotomaria Adansoniana. $. shorter ntoh, <q di Suoy- 
= «na (Fig. 289), also ob- 
tained living by the * Blake.” 
Among other univalves, the Mar- 
ginellide are represented by such 
species as Marginella succinea Con- 
rad, extending from shallow water 
to several hundred fathoms, and M. 
Watsoni (Fig. 290), characteristic of 
great depths. The Ringieulidz, of 
which many species are known fossil, * 
are illustrated by JR. leptocheila Fig. 289.— Pleurotomaria Quoy- 
(Fig. 291), described first by Brug- — 
none from the Mediterranean, and afterward from deep water 
Fig. 287. — Leptothyra 
induta. 4. 
