438 RAHD.E. 



spines, each of which has an oval osseous base ; the margin of 

 the base entire, with a central projecting crooked shank or 

 spine directed backward. Two of these broadly-based spines 

 occupy the central ridge of the nose ; others, to the number 

 of thirteen or fourteen, are distributed over each side with 

 some regularity, and similarly disposed on the two sides. 

 The dorsal ridge of unequally-sized spines begins a short dis- 

 tance between and behind the temporal orifices, one or two 

 small spines occurring between each of the larger ones : this 

 single line of spines extends to the origin of the tail, where 

 three rows of spines begin and are continued along it, forming 

 a series of powerful weapons. The tail is furnished with two 

 membranous fins on the upper central ridge, and ends with a 

 small dilatation. The prevailing colour of the upper part is 

 brown, with numerous lighter-coloured spots, and sometimes, 

 as has been noticed already, with one larger rounded spot on 

 each pectoral. Young males and females have fewer spines 

 on the body than old males, and both sexes attain some size 

 before they put forth any ; they have frequently also but one 

 row of spines along the tail. The colour of the under side 

 is pure white, with a few spines only on each side. The teeth 

 of the adult male in this species are decidedly different from 

 those of the female, as shown in the woodcut at the top of 

 page 416 ; those represented on the left hand being from a 

 male fish, and those on the right from a female fish of the 

 same size, and representing one-half of the inside of the 

 mouth of each as seen from behind. 



