Mr. W. Thompson on the Irish Coregoni. 421 



Coregonus clupeoides, Nilss. ? Plate XVI. fig. 4. 



By the continued kind attention of the Rev. C. Mayne, 

 (Vicar- general of Cashel), a second specimen of this fish, taken 

 in the river Shannon near Killaloe, was forwarded to me on 

 the 9th of November last. This individual, being quite per- 

 fect, enables me now to supply a figure of the species, and to 

 offer some further remarks upon it. On comparing it in every 

 character with my description of the individual first obtained 

 ^Annals' for Dec, p. 267, which was divested of its scales, 

 and injured in some of the fins, I find very few additional ob- 

 servations to be requisite. Its length is 4f inches, depth 10^ 

 lines ; number of scales on lateral line, and from it to dorsal 

 and ventral profile as described in last, judging in that in- 

 stance from their impressions merely ; the scales rounded at 

 the posterior margin, and smaller than in any other British 

 Coregonus. D. 14 ; P. 16 ; V. 1 + 1 1 ; A. 14 ? C. 20|| = Br. 9. 

 In the dorsal, the 4th and 5 th rays longest, and of about equal 

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

 the 1st 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 below it pale yellow- 

 ish-olive when viewed in the shade, but with the light striking 

 on it, of a delicate silveiy 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 institute a comparison of the chief differ- 

 ences between this species and Cor. Willughbeii, the only 

 other British fish of the genus having the lower jaw exceed- 

 ing 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. Willughbeii is closed, 

 the point of the lower jaw is so elevated as to be on a hne 

 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 mar- 



