THREE-sriNED STICKLEBACK. 175 



through the middle of it; and on each side of the origin of 

 this flat i^late or ventral shield, (which in some degree serves 

 the purpose of a sternum, as well as a defensive armour for 

 the breast,) is a sharp spine of considerable length, and 

 finely serrated on its upper border or edge. This formidable 

 spear is in fact one of the two which serve to sj)read the 

 membrane of the ventral fins, but it is the weapon with which 

 all the deadly contests of this fish are conducted. There is a 

 slight spine in front of the anal fin. The dorsal and anal 

 fins are on the hinder part of the body; and the origin of 

 the latter is a little behind that of the former. The body 

 grows slender as it approaches the tail, the latter organ in its 

 folded state being concave. When dry the plates or shields 

 before mentioned appear rough. Colour of the back olive 

 brown, well defined on the sides; below, and on the fins and 

 tail a dull yellow: the colours influenced, no doubt, by the 

 spirit in which these fishes had been preserved. Formulae of 

 the fin rays, — pectoral ten, dorsal fifteen or sixteen, ventral 

 two, caudal eleven, with some small rays. 



Another example of the same variety, and about the same 



length, was of a much more slender form, and in other 

 respects, diffierent proportions, the dorsal and anal fins being 

 also carried nearer to the tail; and in a third, which may be 

 termed the Half-armed Stickleback, while the depth of body 

 nearly answers to the example we first described, the dorsal 

 and anal fins are reduced to much smaller dimensions, there 

 is an elevated ridge near the side of the tail, and the tail 

 itself is straight. The lateral plates in this variety never 

 descend to join with the shield of the belly, and contract 

 suddenly in dimension opposite the third dorsal spine. The 

 colour of these fishes partakes of every variety, from sober 

 brown to a brilliant "-rccn, with rcdtlish or crimson tints. 



