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, Di/tiscus marginalise from its 

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

 water MoUusca. One Dytisciis^ 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 (Ilerpestes fasciatics) 

 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 (3Iacacus cynomolgiis) 

 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 (t^^uncata and arenaria^^ digging them out of 

 the sand, in which they live buried at a depth of about 1^ 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 MoUusca of various kinds. 

 The cat-fish (Chimaei^a^ 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 man}^ as from 30 to 40 

 specimens of Buecinum 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. humphreysia^ium^ 

 Fusus f 6716 stratus., 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 GossijJ, 1889, p. 280. 2 Noack, Zool. JB. ii. p. 254. 



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



