102 Mr. Thompson on the species of Stickleback 



pected, the largest were invariably found where the tempera- 

 ture was lowest, specimens there (G. brachycentrus) not un- 

 commonly attaining the length of three inches, and perfectly 

 free from the pearl-like tumours, which, adhering to the body, 

 infest those inhabiting the comparatively warm waters of the 

 lower grounds. This short-spined Stickleback here exhibits, 

 in all respects, the same colours as the most common of the 

 English varieties ; of many of the larger individuals captured 

 in the month of September, about the one-half were red on the 

 under parts. In large shoals too 1 have remarked fully this 

 proportion to have assumed the scarlet, and in the early sum- 

 mer months have observed that full-grown fishes, in which the 

 most intense shade of this colour prevailed, never appeared to 

 be with spawn*, very few in that state being so much as 

 faintly tinged with it. This Gasterosteus and the Trout (Salmo 

 Fario) seem not to co-exist in some of our smaller rivers, or 

 do so very partially. In the stream whence the largest of these 

 were taken, trout {Salmo Fario) were a dozen years ago very 

 common, and the Stickleback unknown, and it is only since 

 the almost total disappearance of the Trout that this fish has 

 been established in its waters. In a similar stream issuing 

 from the same mountain-range at about four miles distance, 

 the Trout yet maintains its place, and in the parts of the river 

 frequented by it I have in vain looked for the Stickleback. 



The figure of G. brachycentrus in the ^ Hist, des Poiss.^ re- 

 sembles the Irish fish when in spawn, and not its usual ap- 

 pearance. 



In addition to that fish, there is another 3-spined Stickle- 

 back, brought by M. Savigny from the brooks of Tuscany, 

 described as new in the ' Hist, des Poiss.^ — from its brilliant 

 operculum, it is named G. argyropomus. In this and the other 

 characters assigned to it, Irish specimens in my possession 

 fully accord. It is suggested, indeed, with reference to the 

 characters attributed to this and the two other Gasterostei — 

 G. brachycentrus and G. tetr acanthus — brought by M. Sa- 

 vigny from Tuscany — " Nous allons les indiquer, pour en- 

 gager les observateurs a s'assurer de leur constance,^^ p. 498. 

 In the next page it is however remarked of G. brachycentrus, 

 that there is no doubt of its being a true species f. 



Four-spined Stickleback, G. spinulosus, Yarr. and Jenyns. 

 Among specimens of Gasterostei kindly procured for me at 



* So late as the 19th Sept. 1832, I remarked one large with spawn. 



t The different varieties of the 3-spined Stickleback ai*e commonly known 

 in the North of Ireland by the name ofSpricklebag — evidently a corruption 

 of the proper term — Pinkeen is applied to them in the South ; and from the 

 Shannon they have been sent me under the name of Thornback. 



