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 XL, 

 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, 9 and 10) is paved. The Neomenians, Lamel- 

 lariidse, and some Nudibranchs, browse on the 

 corals, sponges, and tunicates. The Chsetoderms 

 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), 

 C armaria (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 



