96 Mr. Thompson on the species of Stickleback 



to Dr. J. D. Marshall, who submitted them to my inspection,) 

 I find that in some the lateral plates extend throughout the 

 entire sides, as in G. trachurus ; in others, so far only as in 

 G. semiarmatMS ; and in some again no further than in G. 

 lieurus. No other difference can be perceived in these speci- 

 mens, which are all of a small size, from an inch to an inch 

 and a half in length. From between tide-marks in Larne 

 Lough (Mrs. Patterson) ; from oozy and rocky pools over 

 which the tide regularly flows, situated near the edge of Bel- 

 fast Bay (Richard Langtry, Esq. — W. T.) ; also from a deep 

 pool in the middle of it (Mr. James Nichol) — and from the 

 harbour of Donaghadee (Capt. Fayrer, R.N.)., 1 possess ex- 

 amples of the full-armed Stickleback of various sizes up to 3 

 inches. 



In addition to these Irish examples of the full-armed Stickle- 

 back, some 2 inches in length from the Thames, communicated 

 in 1 834 by Mr. Yarrell, are before me for comparison, and se- 

 veral from 1^ to 1} inch, which I obtained in a marine rock- 

 pool at Ballantrae, Ayrshire, in August 1839. 



In June 1836, Lieut. Davis, R.N., sent to the Belfast Mu- 

 seum, from the neighbourhood of Donaghadee, some gigantic 

 specimens, two of which are 3|^ inches in length and 10 lines 

 in depth ; a third is 3 inches 4 lines long and 9 lines deep ; 

 the number of fin-rays is the same in all, viz. 



D. Ill + 12 ; A. I + 9 ; P. 10 ; V. I + 1 5 C. 12. 



These three individuals have each 23 plates on the side of the 

 body to the origin of the caudal keel, and thus agree w ith the 

 G. semiloricatus. Colour as usual in female specimens, no red 

 appearing anywhere. With the above were tw o others of or- 

 dinary size ; one of which was red on the lower portion of 

 the body. Lieut. Davis stated in a note respecting them, 

 that they " were found in a pool of brackish water access- 

 ible to the sea, at the Foreland rocks near Donaghadee.^^ 

 The example, 2^ inches in length, from deep water in Belfast 

 Bay, differs very much from the large individuals just noticed, 

 in the free margins of the lateral plates ; these, in the latter are 

 finely, regularly, and very minutely serrated, w^hile in the former 

 they are distinctly toothed, the denticles becoming larger on the 

 plates as these latter approach the tail. The number of these 

 plates to the origin of the caudal keel is about 23, as in the large 

 examples — this number likewise appears in the Thames speci- 

 men of G. trachurus. With the exception of a ray less in the 

 anal fin, the number of fin-rays is the same in that under 

 consideration as in the large fish. The example, 2 inches in 

 length, from Donaghadee harbour, has likewise about 23 



