624 Bashford Dean Memorial Volume 



AN ADULT MALE CHLAMTDOSELACHUS 



An adult male frilled shark is accurately portrayed in Figure 53, plate VI. In the 

 original drawing, this figure is 538 mm. (21.2 in.) in total length. From the fact that this 

 drawing shows the mouth closed, one gets a clear idea of the great length of the jaws 

 which reach to a point well behind the rear of the skull. For measurements of the jaws of 

 four adult specimens of Chlamydoselachus, see Gudger and Smith (1933, p. 268). The 

 extraordinary structure and functioning of the jaws of this shark have been admirably 

 characterised by Goodey (1910, p. 550) as follows: 



Perhaps the most important point in regard to the specialization of the skull of Chlamydo- 

 selachus is to be seen in the extreme length and mobility of the jaws. These are exceptionally 

 long, extending from the anterior, almost terminal mouth to a point well behind the posterior 

 limit of the cranium. This extension is remarkable; in fact, one quarter of the total length of 

 the jaws is found in this region, and it is this feature, connected with the exceptional length 

 of the hyomandibular, which gives the jaws their great mobility. Indeed, their disposition 

 relative to the cranium is quite different from that found in any other Selachian whose skull I 

 have been able to examine or to see a figure of It resembles nothing among the Vertebrates 

 so much, perhaps, as the general disposition of the jaws in certain of the Ophidia. 



As seen in Figure 53, plate VI, in the front of the mouth are a few teeth, and above 

 and sHghtly lateral is the vertical nostril with two divisions — the upper for ingress and the 

 lower for egress of water. The gill'covers are normal, and it can be seen that the first pair 

 flare widely and are continuous across the throat. Short external gill'filaments are seen 

 in every slit as in the female on this plate. The lateral line runs straight back to the re' 

 gion of the dorsal fin where the usual (normal?) irregular bendings are found. The body 

 cavity of the male is plainly not nearly so large as that of the female, nor is the tro- 

 peic'fold region so well marked. On the other hand, the myomeres in the body of the 

 male are distinct whereas none are shown on the trunk of the female. 



The above are, however, but minor differences. The one particular thing, that at 

 a glance differentiates this and all other male individuals from the females, is the presence 

 of the myxopterygia or claspers. As shown in Figure 53, plate VI, these are grooved 

 finger'like modifications of the hinder and inner parts of the pelvic fins. When the male 

 inserts these into the cloaca of the female during copulation, he holds her fast for the 

 passage of the spermato2;oa. It is not necessary here to go further into the structure and 

 function of these organs. These matters have been treated earlier in this article. This 

 drawing is the best representation of the male Chlamydoselachus ever published. 



There is another structure in which these particular drawings of the two sexes 

 differ — i.e., in the end of the caudal fin. In the female the tail and tail fin — as properly 

 restored — end in a fine point. And so do the caudal fins of most of the embryos studied. 

 On the other hand the drawing of the tail fin of the adult male ends in a rounded point 

 and there is a notch near the tip of the ventral lobe. Thus from these figures one might 

 jump to the conclusion that the female fish have pointed caudals and the males notched 

 ones. But this is not true. Gudger and Smith (1933, pp. 293-297) have gone rather fully 

 into the question of the form of the tip of the tail in the frilled shark, reproducing every 



