STICKLEBACKS. 83 



Val. — will be particularly treated of, and come first under notice, as one 

 of the two varieties which are protected with scaly plates throughout the 

 sides. 



G. trachuriis, Cuv. and Val., t. iv. p. 481. 



G. semiloricatus, Cuv. and Val., t. iv. p. 494. 



March 20, 1835. — On examination of a number of 3-spined Sticklebacks 

 from the island of Kathlin (sent by ]\Irs. Gage to Dr. J. D. ]Marshall, who 

 submitted them to my inspection), I find that in some the lateral plates 

 extend through the entii'e sides, as in G. trachiirus ; in others, so far only 

 as in G. semiarmatus ; and in some again no further than in G. leiuriis. 

 No other difi'erence can be perceived in these specimens, 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 Hows, situated near the edge of Belfast Bay 

 (Richard Langtry, Esq. — W. T.) ; also from a deep pool in the middle of 

 it (Mr. James Nichol) ; and from the harbour of Donaghadcc (Capt. 

 Fap-er, R. N.), — I possess examples of the fidl-armed stickleback of various 

 sizes up to 3 inches. 



In addition to these Irish examples of the full-armed stickleback, some 

 2 inches in length ftom the Thames, communicated in 1834 by Mr. 

 Yarrell, are before me for comparison, and several from 1^ to 1| inch, 

 which I obtained in a marine rock-pool at Ballantrae, Avrshire. in August, 

 1839. 



In June, 1836, Lieut. Davis, R. N., sent to the Belfast Museum, from 

 tiie 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 ; 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 with the G. semiloricatus. 

 Colour as usual in female specimens, no red appearing anywhere. With 

 the above Avere two others of ordinary 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 Avater accessible 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 seri'ated, while 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 specimen 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 I )onaghadee harbour, has likewise about 23 plates 

 on the side to the origin of the caudal keel : the serration on the free 

 margin of these plates is intermediate between that exhibited in the speci- 

 mens 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 difi"erences are observable, as — considering for 

 the present adult fish onlv — in the comparative length of the dorsal and 



G 2 



