Ill ENEMIES OF SLUGS AND SNAILS 59 



in their mandibles, and then, throwing their head backwards, 

 break the shell by striking it against their prothorax. 



The common water beetle, Dytiseus marginalise from its 

 strength and savage disposition, is a dangerous enemy to fresh- 

 water Mollusca. One Dytiseus^ kept in an aquarium, has been 

 noticed to kill and devour seven Limnaea stagnalis in the course 

 of one afternoon. The beetles also eat L. peregra^ but appar- 

 ently prefer stagnalis^ for when equal quantities of both species 

 were placed within their reach, they fixed on the latter species 

 first.i 



In East Africa a species of Ichneumon (Herpestes fasciatus) 

 devours snails, lifting them up in its forepaws and dashing them 

 down upon some hard substance. ^ In certain islands off the 

 south coasts of Burmah, flat rocks covered with oysters are laid 

 bare at low tide. A species of Monkey (Macacus cynomolgus) 

 has been noticed to furnish himself with a stone, and knock the 

 oysters open, always breaking the hinge-end first, and then pull- 

 ing out the mollusc with his fingers.^ 



The walrus is said to support himself almost entirely on two 

 species of Mya (truncata and arenaria')^ digging them out of 

 the sand, in which they live buried at a depth of about IJ feet, 

 with his powerful tusks. Whales swallow enormous numbers 

 of pelagic molluscs (Clio^ Limacina^, which are at times so 

 abundant in the Arctic seas, as to colour the surface for miles. 

 Many of the larger Cetacea subsist in great part on Cephalo- 

 poda ; as many as 18 lbs. of beaks of Teuthidae have been taken 

 from the stomach of a single Hyperoodon. 



Fish are remarkably partial to Mollusca of various kinds. 

 The cat-fish (Chimaera^ devours Pectunculus and Cyprina^ 

 crushing the stout shells with its powerful jaws, while flounders 

 and soles content themselves with the smaller Tellina and Syn- 

 dosmya which they swallow whole. As many as from 30 to 40 

 specimens of Buccinum undatum have been taken from the 

 stomach of a single cod, and the same 'habitat' has been re- 

 corded for some of the rarer whelks, e.g. Bucc. humphreysianum, 

 Fiisiis fenestratuSy the latter also occurring as the food of the 

 haddock and the red gurnard. No less than 35,000 Turtonia 

 mimita have been found in the stomach of a single mullet. 



1 J. W. Williams, Science Gossip, 1889, p. 280. 2 Noack, Zool. JB. ii. p. 254. 



3 La Naturey xv. (2) p. 46, 



