CARASSIUS OBLONGUS. 109 



That all these differences are due to food and habitat, so that the same 

 stock in a lake develops into the Crucian Carp, and in a pond into the 

 Prussian Carp, would seem highly probable when we notice the close similarity 

 of fin structure and scales. Its distribution is like that of the Carassius 

 vulgaris. The Swedes term it Damm-Rtida, or Pond Crucian, to distinguish 

 it from the Common Crucian, or Lake Crucian (Sjo-Ruda) . 



Carassius vulgaris, var. oblongns (Fig. 44). This was regarded as a distinct 

 species by Heckel and Kner, on account of its more elongated form, flatter 

 back, large thick head, larger eye, and longer and more pointed tail. The 

 length 'of the body is two aud-two-third times as much as its height. Its 



Fig. 44. CARASSIUS OBLONGUS (HECKEL AND KNEK). 



greatest breadth at the operculum is one-half of the height of the body. The 

 eye is larger than in any other variety, its diameter being one-fourth of the 

 length of the head ; its own diameter separates it from the extremity of the 

 snout, and there is an interspace of only one and a half times the orbital 

 diameter between the eyes. The snout is more pointed than in other varieties, 

 and the contour from the mouth to the back is very slightly arched. The 

 dorsal fin commences in the anterior half of the length, and extends for fully 

 one-third of the length of the body. Its bony ray is conspicuously serrated 

 on its hinder border, rather feeble, and as long as the jointed rays which suc- 

 ceed it. The anal fin is deeper than long, and its commencement is anterior 

 to the termination of the dorsal. The ventral fins are placed half-way down 

 the body behind the commencement of the dorsal fin ; they are somewhat 

 elongated, and reach the vent. The pectoral fins have also an elongated aspect, 

 and they reach back to the ventrals. 



