loo Mr. Thompson on the species of Stickleback 



is continued down the sides in the form of regular transverse 

 bands upon a yellow ground; — river Shannon, at Killaloe 

 (Rev. C. Mayne) ;— Youghal, county Cork (Mr. R. Ball). 



From Scotland I have specimens obtained in the neigh- 

 bourhood 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. lieu- 

 rus has occurred to myself. Next to this variety naturally 

 comes the 



G. brachycentrus, Cuv. and Val., t. iv. p. 499, which like it, 

 is smooth along the sides from the pectoral region, but diflfers 

 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 G. brachy- 

 centrus being ever varying. The Irish localities whence I 

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

 along the margin of Lough Neagh (W. T.), Dublin, Youghal, 

 and Portarlington — supplied from these three localities by the 

 friends before mentioned. 



The largest example which has come under my observa- 

 tion was one taken by myself in England, at Stow Pool, 

 Lichfield, in July 1836, and which was noticed in the ^ Pro- 

 ceedings of the Zoological Society' for the next year. This is 

 the only allusion I have seen to the G. brachycentrus in Great 

 Britain. 



This variety, which from the shortness of its spines is the 

 most defenceless of the 3-spined Sticklebacks, we should, 

 a priori, — i. e. if the suggestion respecting the full-armed va- 

 riety be correct — 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.,' where it is stated to have been obtained by 

 M. Savigny in the brooks of Tuscany. 



The following comparison between G. brachycentrus from 

 the neighbourhood of Belfast, and specimens of G. lieurus, &c. 

 from the Thames, favoured me by Mr. Yarrell, was drawn up 

 early in 1834:— 



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

 G. lieurus, the latter being from the centre of the back alike grace- 

 fully 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. 



