THE POLLAX. 1 T-'i 



at the posterior margin, and smaller than in any other British Coregonns. D. 

 14; P. 16 ; V. 1 + 11 ; A. 14? C. 20{|= Br. 9. In the dorsal, the 4th and 5th 

 rays longest, and of about equal length ; the few anterior rays of the pectorals 

 about equal, the first much the stoutest; 4th and 5th longest in the anal, and 

 about equal ; axillary scale of ventrals rather more than one-third their length. 

 Colour of specimen (from spirits), body above lateral line and a short way be- 

 low it pale yellowish-olive when viewed in the shade, but with the light striking 

 on it of a delicate silvery blue, thence to the belly silvery; dorsal and caudal 

 fins marked over the rays and membrane with black points, imparting to them 

 when closed a blackish tinge ; pectorals, ventrals, and anal, excepting a very 

 few black points on last, colourless. 



It is desirable to institme a comparison of the chief differences between this 

 species and Cor. Willughbei, the only other British fish of the genus having the 

 lower jaw exceeding the upper in length. The C. clupeoides differs from this in 

 the mouth being less obliquely cleft, or in having the lower jaw less ascending 

 (when the mouth of C. Willughbei is closed, the point of the lower jaw is so 

 elevated as to be on a line with the upper margin of the pupil of the eye ; in the 

 other it is on a line with the centre of the pupil) ; opercle broader and less 

 rounded off at the base, and with the ascending margin more oblique, in C. clu- 

 peoides ; * its scales very much smaller ; outline of dorsal fin very different, the 

 membrane in this falling considerably short of the points of the rays, and its out- 

 line from the longest ray to the extremity of the tin being somewhat rounded. 

 This comparison was made between two specimens of C. clupeoides ? from 4 to 

 5 inches in length, and two of C. Willughbei about 6 inches long. 



From the continental species. Cor. Maroenula, as described by Bloch (and 

 which, like the C. Willughbei, agrees with that under consideration in the lower 

 jaw being the longer), the C. clupeoides diflers chiefly in having a greater number 

 of rays in the dorsal fin (14 or 15 to 10), in having teeth in the under jaw (on this 

 difference alone 1 should not lay any stress, the teeth being so small as to be 

 easily overlooked), and in the negative character of wanting such an appearance 

 on the lateral line as would come under the description of " garnie de cinqnante- 

 huit points noirs ; " the scales on the back and greater part of the sides are dotted 

 with very minute black points visible under a lens, and of which those on the 

 lateral line have share, but not so many as the row just above, the number of 

 these points gradually decreasing from the back downwards. 



Should this fish eventually prove to be distinct from the C. clupeoides of Nil- 

 sson, I would suggest that the specific name of elegans be applied to it. 



Coregonus Pollan. 



In connexion with the figure C. Pollan now given to accompany that of 

 Cor. clupeoides, the following remarks are offered. The characters in which 

 the pollan differed from the two British species known at the time it was an- 

 nounced were pointed out in the original description. From the two speci- 

 mens since recorded, it may in the first place be stated to differ from C. 

 microcephalus, the Loch Lomond fish, in having the head longer, the fins 

 less (and of a lighter colour), and the scales rather smaller; from the C. clu- 

 peoides the pollan differs in being much larger, in the jaws being equal, f the 

 scales rather larger and in the form of the dorsal fin. 



* The difference in this respect between those two species is not greater than 

 we sometimes see in different sexes of the same species of Salmo: the Core- 

 goni not having been dissected, their sexes are unknown to me. 



f This seems to be the best (/rnf'?-;?^ character ; I have seen some individuals 

 with the upper rather exceeding the lower jaAV, others with the lower slightly 

 projecting beyond the upper, and the difference was not sexual. It is perhaps 

 unnecessary to observe, as it would apply to fishes generally, that other indi- 

 viduals examined vary much in relative proportions from those which served for 

 the original description ; the proportion of head to depth of body, it is obvious, 

 must vary in the sexes at particular pejiods ; that of head to entire length I 



