FOOD, HABITS, ETC. 69 
the Murex as an Oyster-knife. The Bivalve prey, 
generally one of the Ark-Shells, is gripped in the 
powerful foot of the Gastropod and its shell margins 
pressed against the spine till the latter is driven 
between them like a wedge and the valves are forced 
apart, when the Murex can insert its proboscis and 
devour the luckless occupant at leisure. The strange 
spine in a like position in Acanthina (Plate XI., 
Fig. 2) may serve a similar purpose. Sycotypus 
(Plate XXXIL, Fig. 12) can grip a Venus Shell while 
it deliberately chips out an opening with its own 
shell in the margin of the Bivalve. It will also insert 
its own shell between the open valves of the Oyster 
and thus keep the Bivalve Shell open while it devours 
the inhabitant. Scaphander feeds on Bivalves, which 
it swallows whole, crushing them between the 
calcareous plates with which its gizzard (Plate III., 
Figs. g and 10) is paved. The Neomenians, Lamel- 
lariide, and some Nudibranchs, browse on the 
corals, sponges, and tunicates. The Chaztoderms 
and Scaphopoda thrive on minute forms of animal 
life in the ooze and mud which they frequent. 
In the open sea the Pteropods also fare off micro- 
organisms, while Ianthina (Plate XXX., Fig. 2), 
Carmaria (Plate XXVI., Figs. 20-21), and Firola, 
attack the floating Jelly-fish. Carinaria will also 
capture fish, for Mr. Martin Woodward and the 
writer once took from the interior of one individual 
