FISHES 287 



Monk-Fish (Rhina squatind), found all over the world in tropical 

 and temperate seas, and not uncommon on our western coasts. 

 Its chief interest lies in its flattened shape, in which respect it 

 may be regarded as an intermediate stage between the sharks 

 and skates, and in the extremely large pectoral fins (the " wings " 

 of the imaginary angel) which also afford a point of resemblance 

 to the latter group. 



6. Port Jackson Shark Family. — This is a small group of 

 comparatively small forms, including only one genus of four 

 species, of which two are found on either side of the Pacific. 

 The best known is the Port Jackson Shark {Cestracion Philippi) 

 which ranges from Japan south to Australia and New Zealand. 

 The head is short and blunt, and there is a sharp spine in front 

 of each dorsal fin ; but the chief peculiarity is found in the teeth. 

 Those in front are sharp-pointed, but the rest have blunt rounded 

 crowns, and, being arranged in several closely adjacent rows, form 

 a surface well adapted to crush the molluscs upon which the shark 

 feeds. 



7. Comd-tootked Sharks. — This is a small group of tropical 

 and sub-tropical species possessing certain primitive characters. 

 There is only one dorsal fin, and the gill-slits, instead of being 

 five in number on each side, as in other members of the sub- 

 class, are either six or seven. Four of the five known species 

 belong to one genus (^Noiidanus), and one of them, the Grey 

 Six-gilled Shark (A^. griseus), an Atlantic and Mediterranean 

 form, is sometimes taken in British waters. The teeth are 

 elongated, and each of them consists of a series of slanting cusps 

 diminishing in size from one end of the tooth to the other. The 

 other three species of this genus have seven gill-slits on each 

 side. The Japanese Frill-gilled Shark {Chlamydoselache anguinetis), 

 which inhabits very deep water, resembles an eel in shape, and 

 its mouth is at the front end of the body instead of upon its under 

 surface. There are six gill-slits on either side, and each of them 

 is protected by a backwardly-directed fold of skin, pleated in a 

 frill-like manner. 



Order 2. — Skates and Rays (Batoidei) (fig. 167) 



The Skates and Rays which constitute this group are much 

 flattened from above downwards, just the reverse of what obtains 



