THE POLLAN. 
173 
at the posterior margin, and smaller than in any other British Coregonus. D. 
14 ; P.16; V. 1 + 11 ; A. 14? C. 20j§= 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 membrarie 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 institute 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 fin 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 differs 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 I 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 cinqtiante- 
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 these 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 general 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 periods ; that of head to entire length I 
