LEUCISCUS IDUS. 



139 



Leuciscus idus (Liu.). The Ide. 



The fish is known in Sweden as the Id ; in Germany it is the Nerfling ; 

 in Prussia, the Aland. It is the Gose in Silesia, Bratjuck in some parts of 

 Hungary, and the Gangling in Austria. It is placed by Heckel in a distinct 

 genus, named Idus, and in this sub-division of Leuciscus he is followed by 

 nearly all the Continental writers. The larger grouping of Dr. Giinther, 



Fig. 68. LEUCISCUS IDUS (LIXNJEUS). 



however, preserves the species in association with its allies, the Roach, Chub, 

 Dace, Rudd, and Minnow (Fig. 68). 



The body is moderately elongated and compressed ; its height is one- 

 quarter of the length of the fish. The length of the head is only one- 

 sixth of the total length ; the greatest thickness is less than half the height. 



The eye is less than one-quarter of 

 the length of the head ; it is separated 

 from the other eye by twice its own 

 diameter in the mature fish, and sepa- 

 rated from the snout by a single dia- 

 meter. The forehead widens with age. 

 The mouth is small ; the jaws are equal 

 in length, and the angle of the mouth 

 reaches only to the nai*es. The mucus 

 membrane forms numerous folds on 



the throat, and they are covered with delicate papillaa, some of which put on the 

 appearance of teeth. The pharyngeal teeth (Fig. 69) have the formula 5'3 

 3'5. The dorsal pi-ofile is moderately and evenly arched, with a depression 

 at the hinder part of the head ; the ventral outline is similar. 



Fig. 69. PHAHYNGEAL TEETH OF LEUCISCUS 

 IDUS. 



