"^^^^ 



n 



CHIMERA AND ITS CHARACTERISTICS. Iq 



SEXUAL DIFFERENCES. 



In li\ ing specimens it is surprisingly difficult to distinguish the sexes (C collici). 

 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 siiawning 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. '\'\\v 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 Heshy pad lies in 

 the median ventral line behind the pelvic fins, and ]n'o- 

 duces a contour not unlike that of the combined mixii)te- 

 rygia. Closer examination shows slight difierences in the 

 proportions of male and female; thuslc/. fig. i )in tlu' male 

 the eye is relatively of larger size, the snout nn)re obtuse, 

 the fins shorter and wider, the dental plates smaller and 

 often distinguishable in shajK\ 



Dental plates. — In C. colliei the mandibular dental 

 ))lates of the female do not usually exhibit as marked a 

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

 ]>lates are shown in fig. 5 a-i, sketched from jaws of adult 

 females selected at random, and these may be cc^ntrasted 

 with theeommon type of the mandibular plate of the male 

 outlined in fig. 5 j and 1.. Cireat variation is, however, 

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

 (a, c, k, \) have no conspicuous "canine " [irong, two have 

 the inong well marked (n, c), the rest are intermediate. In 

 the males seven plates out of ten wH're found to l)e conspic- 

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

 figured (j, 1.). One specimen (K)only was remarkable for 

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

 number, arrangement, and distinctness of tlu- tritors, and 

 in the general thickness of the dental j)lates. These characters, however, are partly 

 dejiendent 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 



Fig. 6. Dental plates of Chimflera 



A, front view of denial plates of larue 

 8i>ecimcn ( female 1 . 



B, dental plates of same siiecimen, viewed 

 in visceral aspect. 



C, front view of dental plates of male. 

 Observe esi>ecially the asymmetry of the right 

 mandibular plate. 



D, dental plates of same specimen, viewril 

 in visceral as|)ect. 



