20 CHIM/EROID FISHES AND THEIR DEVELOPMENT. 



the plates are stouter and show irregularly worn margins. In somewhat rare cases 

 asymmetry results. Two instances of this kind are shown in fig. 6. In the first 

 (a and b) the upper "incisor" plates are quite different in shape (a female) ; in the 

 second (a male, c and n) the mandibular plates are irregular, one having the typical 

 "canine" prong, the other a fairly straight margin. In visceral aspect one (n) car- 

 ries the median tritors of the palatine plates far forward ; the other (b) is prac- 

 tically without a median tritor. In one (u) the mandibular plates form a symphyseal 

 beak-like prominence; in the symphysis of the other (b) there is a noticeable 

 notch. In general, there is considerable variation in the number of tritors in indi- 

 viduals of apparently the same age. 



The foregoing peculiarities are commented upon, since they show that consider- 

 able judgment is necessary to determine accurately species of Chimsroids when 

 dental plates alone can be studied, c. g., in the case of many fossil forms. Indeed, 

 with so wide a range of variation, it is quite conceivable that C. collici, if known only 

 by its dental plates, might be described under several species, and possibly two 

 genera. The general relations of the dental plates in jjoth living and fossil forms 

 are considered on a later page. 



FEEDING AND FOOD. 



In view of the special character of the dentition of Chimaera, one would nat- 

 urally expect its food supply to be definite in character. The examination of the 

 contents of its gut, however, showed ( C. collici) singularly omnivorous habits. It 

 is true that the broken shells of mollusks are commonly found, as well as fragments 

 of good-sized crustaceans, as indeed the scanty literature records. Thus, in the gut 

 of C. vionstrosa Faber finds crustacean and shell-fish fragments; Alonticelli, quoting 

 Liitken, Cvprina islandica ; and Olsson, broken shells {Lcda and J'niiis) and bits of 

 large decapods. Olsson finds also (and his observations are the most detailed 

 hitherto published on the feeding of Chimaira) chsetopods, amphipods, echinoids, 

 and pol3'ps. 



In C. collici observations on about a score of individuals showed a singular 

 mixture of foods. Most numerous were vertebral columns of small isospondylous 

 fishes, a few mollusk shells, usually greatly crushed, a quantity of sand and fine 

 gravel, squid, nudibranchs and opisthobranchs, bits of cases, jaws, and sets of 

 annelids, and occasionally a fragment of a crustacean. In one instance the gut was 

 filled with seaweed. One is not surprised, therefore, that this species is taken 

 readily with various baits. In Puget Sound it is fished with mussel, clam, prawn, 

 sandworms, and even salt pork. At Monterey the greatest numbers were taken 

 with squid; failing this, trawls were baited with herring, fresh or salted. 



A curious feature in connection with the feeding conditions of Chim^era is that 

 in so many specimens examined the gut is found entireh' empty, even at the time 

 the fish is taken from the w^ater. This condition has been commented upon by 

 several authors, among others by P. J. Van Beneden and Olsson, the latter finding 



