XVII ELASMOBRANCHII—-HOLOCEPHALI 4690 
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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 Chimaera (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 retractile 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 
Fic. 267.—Chimaera monstrosa (male). im, Mouth ; x.p, frontal clasper ; 
op, operculum. 
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 first 
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) colliet 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. 
