CHIMERA AND ITS CHARACTERISTICS. 



SEXUAL DIFFERENCES. 



In living specimens it is surprisingly difficult to distinguish the sexes (C colliei}. 

 The secondary sexual characters of the male are then inconspicuous, and one is apt 

 to identify it rather by its smaller size and by its slightly darker tone. Breeding 



colors are not marked, but at the time of spawning the 

 female shows considerable color in the anal and caudal 

 regions, the fins especially being suffused with blood. 

 In males, those, it appears, are in breeding colors in 

 which the anterior rim ~of~ the pelvic fins and the ante- 

 rior region of the pectoral fins are the whitest. It is 

 difficult to distinguish the claspers. The frontal organ is 

 folded neatly away below the surface of the head ; the 

 mixipterygia are closely apposed to the trunk, hardly mod- 

 ifying the contour of this region ; the anteropelvic claspers 

 are tucked into their dermal pouch, and the mouth of the 

 pouch is nearly closed. In the female a fleshy pad lies in 

 the median ventral line behind the pelvic fins, and pro- 

 duces a contour not unlike that of the combined mixipte- 

 rygia. Closer examination shows slight differences in the 

 proportions of male and female; thus (cf. fig. i)in the male 

 the eye is relatively of larger size, the snout more obtuse, 

 the fins shorter and wider, the dental plates smaller and 

 often distinguishable in shape. 



Dental plates. In C. colliei the mandibular dental 

 plates of the female do not usually exhibit as marked a 

 prong in the "canine" region as the males. Nine such 

 plates are shown in fig. 5 A-I, sketched from jaws of adult 

 females selected at random, and these may be contrasted 

 with the common type of the mandibular plate of the male 

 outlined in fig. 5 j and L. Great variation is, however, 

 apparent in both cases. Of the nine plates figured, four 

 (A, c, E, i) have no conspicuous "canine" prong, two have 

 the prong well marked (D, c), the rest are intermediate. In 

 the males seven plates out of ten were found to be conspic- 

 uous in the "canine" prong, quite similar to the specimen 

 figured (j, L). One specimen (ic)only was remarkable for 

 the evenness of its edge. Variation was also marked in the 

 number, arrangement, and distinctness of the tritors, and 

 in the general thickness of the dental plates. These characters, however, are partly 

 dependent upon the age of the fish. In the young the plates are more delicate 

 and regular, and when viewed against the light they are less apt to show tritoral 

 lines. When the latter appear they are slender and translucent. In large specimens 



D 



Fig. 6. Dental plates of Chimaera 



A, front view of dental plates of large 

 specimen ( female ) . 



B, dental plates of same specimen, viewed 

 in visceral aspect. 



C, front view of dental plates of male. 

 Observe especially the asymmetry of the right 

 mandibular plate. 



D, dental plates of same specimen, viewed 

 in visceral aspect. 



