SMOOTH-HEADS AND SOUTHERN SALMON. 491 



The common anchovy of the Mediterranean (Enqraulis encras- 

 Anchovies. 



sichoLus) is the typical representative of a second widely-spread 



genus, with over forty species, differing from the last by the more or less nearly 

 conical muzzle projecting beyond the lower jaw, and also by the eyes being covered 

 with skin ; while the cleft of the mouth is deep, and the tail-fin forked. In most 

 cases each side of the body is ornamented with a broad longitudinal silvery stripe. 

 The common anchovy is met with off the south-western coasts of England, but 

 wanders still further to the north, and serves to supply the markets of the world. 

 Some species have the rays of the pectoral fins produced, and thus lead on to the 

 allied Oriental genus Coilia, in which the foremost rays of these fins are fila- 

 mentous, and the exceedingly long anal fin extends backwards to join the caudal. 

 A very distinct group, which, as already mentioned, is regarded 

 by some as a distinct family, is typically represented by the two 

 species of the tropical and subtropical genus Elops. In addition to the characters 

 of the skull noticed in p. 487, these fish have the lower jaw longer, a thin plate of 

 bone extending backwards from the point of union of the two branches of the 

 lower jaw, and the whole under surface of the body smooth and rounded. The 

 common species grows to a yard in length. An allied type (Rhacholepis) occurs 

 in the Cretaceous rocks of Brazil. 



The earliest allies of the herring tribe seem to be the extinct 

 Slender- Scales. 1 . . ° 



slender-scales {Leptolepididai), of which there are a considerable 



number of species, ranging throughout the Jurassic period. In the typical 



Leptolepis the dorsal fin is placed immediately over the pelvic pair, but in the 



nearly allied Thrissops it is over the anal. Although there are a number of other 



extinct generic types, more or less closely related to the herrings, it is impossible 



to enter into their consideration here, and we accordingly pass on to 



BLACK SMOOTH-HEAD (^ liat. size). 



The Smooth-Heads and Southern Salmon. 



Families Alepocephalid^e and Haplochitonid^e. 



The first of these two families is typically represented by the 



genus Alepocephalus, of which a species (A niger) is shown in the 



annexed illustration. While agreeing with the typical salmonoids in the structure 



