found in Ireland. 9f 



plates on the side to the origin of the caudal keel : the serra- 

 tion on the free margin of these plates is intermediate be- 

 tween that exhibited in the specimens from the Foreland Point 

 and the one just noticed from Belfast Bay. 



In the full-armed Sticklebacks from the localities generally, 

 which have been enumerated, great differences are observable, 

 as — considering for the present adult fish only — in the com- 

 parative length of the dorsal and ventral spines, and in the 

 lateral plates. In some individuals these do not occupy more 

 than the central portion of the sides, in others the whole sides, 

 and again are intermediate. 



In the absence either of a specimen for comparison, or a 

 figure to refer to, it may perhaps be considered that certainty 

 cannot be arrived at respecting G. semUoricatus. This fish is 

 stated to diflfer from G. tradmriis in having only 22 or 23 

 plates on each side to the origin of the caudal keel instead of 

 its 25 or 26, and in the shoulder-plate (plaque de I'epaule) 

 being larger. It has been seen that some of my specimens, 

 and of these, some of the largest size, possess only the number 

 of lateral plates attributed to G. semUoricatus. In examples 

 of equal length, and from the same as well as fi'om different 

 localities, I find the size of the shoulder-plate to vary like 

 other characters. Hence I am disposed to regard some of the 

 examples under consideration as this fish. 



In the ' Hist, des Poiss.^ it is remarked of G. semUoricatus, 

 " Nous n'avons pu trouver aux environs de Paris que des epi- 

 noches a queue nue ; il nous en est venu de pareilles des de- 

 partemens de la Somme et de I'Oise, de la Rochelle et de 

 quelques autres lieux: nous avons observe celle a queue cuiras- 

 see dans les ruisseaux des cotes de Normandie, et encore re- 

 cemment M. Deslongchamps nous I'a envoyee de Caen, et M. 

 Baillon en a pris dans le Hable-d'Ault, lac saumatre de I'em- 

 bouchure de la Somme, pres du Treport. C'est la seule qui 

 se trouve dans les etangs des environs de Berlin, et elle y est 

 en quantite innombrable. Peut-^tre est-ce I'espece qui habite 

 plus frequemment pres des bords de la mer, et qui pent entrer 

 dans I'eau salee. Des observations ulterieures nous appren- 

 dront sans doute bientot ce qui en est." — /. iv. />. 494. 



This accords generally with my ow^n observation, as in 

 seven out of the nine localities whence my specimens mailed 

 throughout the sides were derived — whether they be called 

 G. trachurus or G. semUoricatus — they were taken either in 

 the sea or estuary. The exceptions are the largest speci- 

 mens, which were procured in a " pool of brackish water ac- 

 cessible to the sea ;" and those from Rathlin, obtained in 



Aym. ^ Mag. N. Hist. Vol. vii. H 



