86 ACANTHOPTERYGII. 



brown colour, which is continued down the sides in the form of regular 

 transverse bands upon a yellow ground ; — River Shannon, at Killaloe 

 (Rev. C. Mayne) ;— Voughal, County Cork (Dr. Ball). 



From Scotland I have specimens obtained in the neighbourhood of 

 Portpatrick by Capt. Fayrer, R. N. Examples from the Thames have been 

 favoured me by Mr. Yarrell ; and in the river Leam, at Leamington, 

 Warwickshire, the G. leiurus has occurred to myself. Next to this 

 variety naturally comes the 



G. brachycentnts, Cuv. and Val., t. iv. p. 499, which, like it, is smooth 

 along the sides from the pectoral region, but differs in the shortness of the 

 dorsal and ventral spines. From the comparative length of these spines 

 alone do I distinguish the two varieties, the other characters attributed 

 to 6r. brachycentrus being ever varying. The Irish localities whence I 

 have this fish are the neighbourhood of Belfast, and pools along the margin 

 of Lough Xeagh (^V. T.), Dublin, Youghal, and Portarlington — supplied 

 from these three localities by the friends before mentioned. 



The largest example which has come under my observation was one 

 taken by myself in England, at Stow Pool, Lichfield, in July, 1836, and 

 which was noticed in the Proceedings of the Zoological Society for the 

 next year. This is tlie only allusion I have seen to the G. brachycentrus 

 in Great Britain. 



This variety, Avhich from the shortness of its spines is the most defence- 

 less of the 3-spined sticklebacks, we should, a jmori, — i. e. if the sugges- 

 tion respecting the full-armed variety be cori'ect, — expect to find where it 

 has fewest enemies, and such, according to my very limited observation, 

 is the case. This would seem to be the variety more peculiar to still 

 water, in which it often attains a very large size. The only continental 

 notice of this fish known to me is that in the Hist, des Poiss., Avliere it 

 is stated to have been obtained by M. Savigny in the brooks of Tuscany. 

 The following comparison between G. brachyceHtrus from the neigh- 

 bourhood of Belfast, and specimens of G. leiurus, Sec, from the Thames, 

 with which I have been favoured by Mr. Yarrell, was ckawn up early in 

 1834, and read before the Linnaean Society that year.* 



In the form of outline the Irish fish generally differs much from the 

 G. leiurus, the latter being from the centre of the back alike gracefully 

 sloped on either side to the head and tail, giving that part a handsome 

 and finely-arched appearance : the under side of the body also exhibits 

 more of this form than that of its congener. The back of the Irish species, 

 instead of thus sloping gradually to the centre, is at that part rather flat, 

 and is at least as high where the dorsal fin originates as elsewhere. The 

 Irish fish is in proportion to its depth longer than the G. leiurus, as speci- 

 mens of the latter under 2^ inches in length, when compared with Irish 

 specimens 3 inches long, proved of equal dimensions (8 lines) at the deep- 

 est part. The difference is also strongly marked in the relative breadth 

 of the two species, the Irish maintaining considerable breadth throughout, 

 even to the origin of the caudal fin. The teeth in the lower jaw of the 

 Irish species consist in the centre of about four rows irregularly disposed, 

 but become gradually less numerous towards the back of the mouth, 

 where they terminate in a single line : the upper jaw contains three 

 rows in front, the outer and inner being regular in distribution. In num- 

 ber, the G. leiurus which I examined does not possess so many teeth as 

 that species, but in their arrangement there is little difference. On 



* Phil. Mag. vol. V. 299 (1834). 



