KEY TO THE PRINCIPAL FISHES 193 



u. The snout is not drawn out to form a toothed 



"saw". . . . Guitar-fishes (p. 58). 



uu. The snout is drawn out to form a flat, blade-like 

 rostrum or " saw ", with a row of strong " teeth " 

 on either edge . . . Saw-fishes (p. 60). 

 TT. The head, trunk and the greatly expanded pectoral 

 fins are all united to form a flattened circular, 

 rhomboid or lozenge-shaped disc, from which 

 projects the comparatively feeble tail, 

 v. The disc is normally more or less circular ; the tail 

 is short and stout, with a broad caudal fin ; there 

 are paired electrical organs between the pectoral 

 fins and the head ; the skin is soft and flabby 



Electric Rays or Torpedoes (p. 64). 

 vv. The disc is usually more or less rhomboid or 

 lozenge-shaped, rarely circular ; the tail is more 

 slender ; the caudal fin, if this is present, is 

 small ; there are no electrical organs between 

 the pectoral fins and the head, 

 w. The tail is rather stout, with two small dorsal 

 fins near its extremity ; there is no saw-edged 

 spine on the tail ; the pelvic fins each have a 

 conspicuous notch in their hinder border 



Skates and Rays (p. 67). 

 ww. The tail is narrow, usually more or less whip- 

 like, and with never more than 1 dorsal fin ; 

 there is often a saw-edged spine on the back 

 of the tail (sometimes 2 or 3) ; the hinder 

 borders of the pelvic fins are not notched, 

 x. The front parts of the pectoral fins do not form 

 horn-like appendages at the sides of the 

 mouth. 

 y. There is no dorsal fin in front of the saw- 

 edged spine ; the pectoral fins extend 

 evenly to the extremity of the snout ; 

 there are several rows of small teeth in 

 each jaw Whip-tailed Sting Rays (p. 72). 

 yy. There is a single dorsal fin in front of the 

 saw-edged spine ; the front edges of the 

 pectoral fins are much indented, so that 

 they have the appearance of being missing 

 at the sides of the head ; the teeth in both 

 jaws are large, flat, and form a tessellated 

 pavement 

 z. There are several rows of teeth in each jaw; 

 the coloration of the upper side of the 

 adult is more or less uniform. 



