ELASMOBRANCHII HOLOCEPHALI 



469 



on the dorsal surface in young forms. Dental plates large and 

 thick, including a single pair in the lower jaw and two pairs, 

 vomerine and palatine teeth, above, which combine trenchant 

 edges with well-marked grinding areas. Three genera are known. 

 In Ckimaera (Fig. 267) the mouth and nostrils are ventral, 

 posterior to a bluntly conical snout. Head surmounted in the 

 males by a club-shaped appendage armed with a pad of recurved 

 denticles, the frontal clasper ; there is also an anterior clasper 

 armed with similar denticles and retrattile into a shallow 

 glandular pouch in front of each pelvic fin, in addition to the 

 ordinary clasper behind the fin. The caudal fin consists of nearly 

 equal-sized dorsal and ventral lobes, between which the slightly 



FIG. 267. Chimaera monsirosa (male), m, Mouth ; n.p, frontal clasper ; 

 op, operculura. 



up-tilted caudal axis is prolonged as a long tapering filament : 

 hence the tail appears to be nearly diphycercal. C. monstrosa 

 occurs off the coasts of Europe from Norway to Portugal, includ- 

 ing the Mediterranean, and also in the neighbourhood of the 

 Azores, as far south as the Cape of Good Hope, and eastwards 

 off the coast of Japan. It is the largest of the living 

 species, reaching a length of 3 feet. C. affinis was iirst 

 taken off the coast of Portugal, and subsequently on the 

 North American side of the Atlantic, at depths ranging from 

 200 to 1200 fathoms. C. (Hydrolagus) colliei is restricted to 

 the North Pacific, and is especially plentiful off South-eastern 

 Alaska, and about the wharves at Esquimalt. Unlike most 

 other Chimaeroids this species swims at the surface, and there 

 is no evidence that it is a deep-sea form. In its breeding 

 habits, and in the mode in which its eggs are fertilised, Chi- 

 maera probably resembles the oviparous Sharks and Dog-Fishes. 



