Four dorsal spines.
Four-spined Stickleback, Edinb. New Phil. Journ. Apr. 1831. p. 386. Yarr. Brit. Fish. vol. i. p. 83.
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.