found in Ireland. 99 



amining si)ecimens of all sizes of G. trachurus and of the other 

 varieties also*, but in some places again the different va- 

 rieties are found together and of every sizef. Mr. Yarrell has 

 so noticed tliree of them in the Thames at Woolwich ; and 

 in Rathlin, as before mentioned, they occur together — in the 

 former locality in brackish, in the latter, in fresh water. 



G. semiaj^matus, Cuv. and Val., t. iv. p. 493, appears to be 

 the rarest of the 3-spined Sticklebacks in Ireland. 1 pos- 

 sess specimens from the island of Rathlin, as before men- 

 tioned, and from Wolfhill, in the neighbourhood of Belfast. 

 One example only occurred in the latter locality, where it was 

 taken in 1832 with a number of G. hrachycentrus, the Stickle- 

 back of that district — it is indeed this variety in every respect, 

 except in having the lateral plates extending along the sides 

 so far as in G. semiarmatus ; the other characters assigned to 

 this supposed species in the ' Hist, des Poiss.^ are very va- 

 riable. From the half-armed species I turn to the 



G. lieurus, Cuv. and Val., t. iv. p. 487, in which the lateral 

 plates do not extend beyond the pectoral region. In every 

 respect but this, it is considered in the ' Hist, des Poiss.^ so 

 similar to G. ty'admrus, that the one description is given as 

 equally applicable to both. The G. lieurus would seem to be 

 the most coxnxnon freshwater Stickleback in Ireland J. 



The localities whence specimens of this fish are now before 

 me, are — the island of Rathlin ; — the neighbourhood of Bel- 

 fast (W. T.) ; — river Bann at Toome (W. T.) ; — Portaferry and 

 Newcastle, county Down (W. T.) ; — Lough Melvin, county 

 Fermanagh (W. T.) ; — neighbourhood of Dublin (Mr. R. 

 Ball); — Glendalough, county Wicklow (Mr. G. C. Hynd- 

 man); — Portarlington, Queen's-county (Rev. B.J. Clarke) ; — 

 some of the examples from this locality are very handsomely 

 marked, being along the back of a rich brown colour, which 



* The partial exception to this is in G. hrachycentrus, in whicli the dorsal 

 spines are comparatively longer in young than in adult individuals, and 

 hence the young in this respect accord with G. lieurus. I here speak of 

 localities in which all the full-grown fish are G. hrachycentrus. 



f From the many small examples of all the varieties about nine lines in 

 length that have come vmder my observation, I should think the number of 

 lateral plates they are to possess through life is then as decided as the num- 

 ber of fin-rays ; i. e. provided they would have remained in the locality 

 whence they were taken. Whether such a change of habitation, as from 

 fresh water to the sea, would cause the smooth-sided at any age to put on 

 the lateral armour, may remain a question. 



X From drains which are occasionally replenished by the tide I have also 

 taken it. 



H2 



