366 MANUAL OF ZOOLOGY SECT. 



(p. 341). Along each side of the head and body runs a 

 faint depressed longitudinal line the lateral line. 



As in Fishes in general, two sets of fins are to be 

 recognised the unpaired or median fins, and the paired or 

 lateral. These are all flap-like outgrowths, running vertically 

 and longitudinally in the case of the median fins, nearly 

 horizontally in the case of the lateral : they are flexible, 

 but stifrish, particularly towards the base, owing to the 

 presence of a supporting framework of cartilage. Of the 

 median fins two the dorsal are situated, as the name 

 indicates, on the dorsal surface : they are of triangular 

 shape ; the anterior, which is the larger, is situated at about 

 the middle of the length of the body, the other a little 

 further back. The caudal fringes the tail : it consists of a 

 narrower dorsal portion and a broader ventral, continuous 

 with one another round the extremity of the tail, the ventral 

 portion divided by a notch into a larger, anterior, and a 

 smaller, posterior lobe. The tail is heterocercal, i.e., the 

 posterior extremity of the spinal column is bent upwards 

 towards the dorsal portion of the caudal fin. The ventral 

 or so-called anal fin is situated on the ventral surface, 

 opposite the interval between the anterior and posterior 

 dorsals ; it resembles the latter in size and shape. 



Of the lateral fins there are two pairs, the pectoral and the 

 pelvic. The pectoral are situated at the sides of the body, 

 just behind the head. The pelvic, which are the smaller, 

 are placed on the ventral surface, close together, at the 

 junction of the trunk with the tail. In the males the bases 

 of the pelvic fins are united together in the middle line, 

 and each has connected with it a clasper or copulatory organ. 

 The latter is a stiff rod, on the inner and dorsal aspect of 

 which is a groove leading forwards into a pouch-like depres- 

 sion in the base of the fin. 





