350 PISCES (OSSE1) ACANTHOPT. [GASTEROSTEUS. 



above each eye, which are always present; teeth varying a little, but 

 generally smaller than in either of the above ; osseous plate behind the 

 opercle generally larger than in the last, but seldom so large as in the 

 Thames specimens; lateral plates varying in number, sometimes ex- 

 tending the whole length of the sides, but generally few, and irregu- 

 larly disposed ; ventral plate about twice as long as broad at the base ; 

 spines varying a little, but always much shorter (the dorsal especially) 

 than in no. 1 ; ventrals equalling half the depth ; sides of the tail, except 

 in one or two instances, not carinated. 



(4.) Specimens from the North of Ireland, procured by W. Thompson, 

 Esq. Of very large size, measuring full three inches. Eyes large, but 

 less than in the Thames specimens ; the space between smooth, with the 

 exception of two deeply impressed lines, one above each eye ; teeth mode- 

 rate ; osseous disk between the opercle and pectoral rather large ; lateral 

 plates five in number, and regularly disposed; ventral plate twice as 

 long as broad at the base, its apex very obtuse ; dorsal and ventral spines 

 strong, but much shorter in proportion than in any of the former spe- 

 cimens, a little curved, their margins finely serrated ; sides of the tail 

 smooth, without any trace of a keel. 



From the above details it will be seen how each character varies in its 

 turn, and at the same time how little connection there is between the 

 variation of one part and that of the others *. 



23. G. spinulosus, Yarr. and Jen, (Four-spined 

 Stickleback.) Four dorsal spines. 



Four-spined Stickleback, Edinb. New Phil. Journ. Apr. 1831. p. 386. 

 Yarr. Brit. Fish. vol. i. p. 83. 



LENGTH. One inch and a quarter. 



DE SCRIPT. Differs in no essential particulars from the last species, 

 excepting in being smaller, and having an additional dorsal spine, situate 

 half-way between the second and third of the ordinary ones ; this spine 

 is very small, and even shorter than that which precedes the soft fin : in 

 my specimen, there are only two lateral plates, and these not very well 

 developed ; they occupy that portion of the side which lies beneath the 

 first and second spines : the ascending plate from the base of the ventrals 

 is longer and narrower than in young specimens of the G. aculeatus of 

 the same size : none of the spines are serrated, and the sides of the tail 

 shew no appearance of a keel : 



D. 4 11; A. 1/10; C. 12; P. 10; V. 1/1. 



Discovered in some plenty near Edinburgh, by Dr. James Stark (to 

 whom I am indebted for a specimen), in September 1830. Possibly a 

 mere variety of the last species, which is said to have been numerous in 

 the same pond. In the number of the spines, it resembles the G. tetra- 

 canthus of Cuvier; but this last is represented as having the spines 

 shorter than in the common species, and the ventral plate broader. 



** Sides naked. 



24. G. Pungitius, Linn. (Ten-spined Stickleback.) 

 Dorsal spines nine or ten. 



* It is more than probable that some of the other foreign Gasterostei described by Cuvier are 

 mere varieties of this species. They hardly differ more from those described above than these 

 last do from each other. 



