AFFINITIES OF CHIMMROIDS Iir 



that it occurs abundantly in the shallow waters of Van- 

 couver ; it is there well known as the " rat fish," and may 

 often be seen in the neighbourhood of the docks, swim- 

 ming slowly at the surface. 



The shape of the body of Chimaera seems in some re- 

 gards to have diverged from the more shark-like form of 

 Callorhynchus. Its organs have become concentrated in 

 the pectoral region, and the disturbance in the curve 

 normals of the fish seems to have caused the shortening of 

 the snout, and the sudden dwindling of the hinder trunk 

 region; the tail, with its thread-like terminal, the opis- 

 thure (Fig. 120), is accordingly to be looked upon as de- 



Fig. 120. Chimcera monstrosa, 3. Juv. X about H. (After L. AGASSIZ.) 

 The anterior ventral clasper is noted at X; the tail terminates in a thread-like 

 opisthure. 



generate. In the anterior region, however, a number of 

 what seem to be primitive characters have been retained; 

 the mucous canals are groove-like ; and the dental plates 

 (Figs. 109, 109^) exhibit a series of tritoral areas. 



Affinities 



All that is known of Chimaeroids, living or fossil, gives 

 but little definite knowledge of the kinships or evolution 

 of the group. Their shark-like structures cannot be shown 

 to have taken their origin from shark-like conditions. 

 Thus the dental plates even of the most ancient forms 

 do not suggest their derivation from shagreen cusps ; the 



