34 E. LÖNNBERG, THE ICHTHYOLOGY OF THE CASPIAN SEA. 



bnt its (lepth is not so large, not niuch exceeding a fourth 

 of the length. As I did not obtain any young or halfgrown 

 specimens of this kind it is difRcult to say in which direction 

 the development has gone. If ouly the largest specimens of 

 the two other species are taken into accoiint it seems as if 

 Kessleri shonld resemble caspia in having a rather short prse- 

 orbital region, and beeause the ventral åns are inoved well 

 forward a short prfeabdominal portion, and a comparatively 

 low dorsal fin. On the other hand, the postorbital region is 

 larger in some instances than in caspia and this is a resembl- 

 ance to saposlmiliovi. The maxillary of Kessleri is smaller 

 than that of the other species. 



A comparison between C. caspia and C. sapjoshnikovi in- 

 dicates that they are rather similar with regard to their re- 

 lative dimensions. The former has, at least in younger stages, 

 a somewhat larger head and greater depth of body. The 

 depth of the candal pednncle which is decreasing with age 

 in caspia is also greater in this species. The postorbital length 

 of caspia is decreasing with age but in saposJinilovi it seems 

 as if the contrary took place, although irregularly and with 

 much variation. The comparative size of the eye is also de- 

 creasing with age in caspia, in saposhnihovi the size of the eye 

 varies a good deal as will be discussed låter. In the former 

 the distances from the snout to the dorsal fin, and to the 

 ventral fins decrease, although irregularly, with age, but this 

 is not conspicuous in saposhniTiovi. Tfce length of the base of 

 the anal and dorsal fins seem to increase with age, but the 

 heighth of the latter to decrease in caspia. But in siiposhni- 

 kovi the variation seems quite irregular. The length of the 

 maxillary decreases in both species. 



The great and as it seems rather irregular variation of 

 C. suposliniliovi seems to indicate that it is a form which has 

 not yet obtained stability in its development. The extreme 

 varieties are strikingh^ different in appearance, but it is not 

 possible to get an}^ sharp limits between them although tw^o 

 difi'erent groups of varieties may be recognized, as may be 

 seen from the following table. 



