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. tracliurus, 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 Rathlin (sent by Mrs. Gage to Dr. J. D. Marshall, who 
submitted them to my inspection), I find that in some the lateral plates 
extend through the entire sides, as in G. tracliurus ; in others, so far only 
as in G. semiarmatus ; and in some again no further than in G. leiurus. 
No other difference 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 flows, 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 Donaghadee (Capt. 
Fayrer, R. N.), — I possess examples of the full-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 from the Thames, communicated in 1834 by Mr. 
Yarrell, are before me for comparison, and several from 1| to If 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 Museum, from 
the neighbourhood of Donaghadee, some gigantic specimens, two of which 
are 31 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. 1 + 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 were 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 water accessible to the sea, 
at the Foreland rocks near Donaghadee.” The example, 21 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, 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. tracliurus. 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 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 differences are observable, as — considering for 
the present adult fish only — in the comparative length of the dorsal and 
