63 MARINE AND FRESHWATER FISHES 



of the normal type. These several varieties have been 



regarded as separate species by many writers, but since 



every gradation between them may be successfully traced, 



they evidently possess no sound claim for such distinction. 



A length of three and a half inches represents the largest 



dimensions recorded of British examples of G. aciileatus. 



A second undoubted freshwater indigenous species is the 



so-called Tinker or Ten-spined Stickleback {Gasterosteus 



pungitius), No. 90, which takes its first name from the 



almost black tint it usually assumes in the breeding season, 



and its second one with reference to the number of spines 



which usually occupy the position of the ordinary first 



dorsal fin. It is the smallest British freshwater fish, it but 



rarely exceeding two inches in length. In habits it closely 



resembles the three-spined species, and in some localities is 



the more abundant of the two. The third British species, 



known as the Sea or Fifteen-spined Stickleback (Gasteros- 



tius spinacJiid), No. 91, is an essentially marine form that 



occasionally ascends rivers into brackish water. With 



reference to its somewhat snake-like contour it is known in 



some localities as the " Sea-Adder," a title, however, 



which is more commonly applied to the Pipe-fishes 



{SyngnathidcB). From five to six inches represents the 



length to which it most ordinarily attains. 



FAMILY XXVII.— Trumpet-Fishes (Centriscidce). 



Body oblong, or elevated and compressed, covered with 

 minute scales, or protected by a cuirass of non-confluent 

 ossifications ; the anterior bones of the skull forming an 

 elongated tube with a small terminal, toothless mouth ; 

 dorsal fins two in number, the first one containing a single, 



