The l^atural History of the Frilled Shar\ 



281 



of Chlamydoselachus, drawn from a comparison between its mouth and gills and those of 

 Cetorhinus and Rhineodon, are likely to be misleading if we neglect to compare the teeth. 

 For the two latter sharks have many thick-set minute teeth, while Chlamydoselachus has 

 relatively few teeth, each with several (3 — 5) slender, recurved barb-Hke cusps or denticles, 

 obviously adapted for holding rather large prey struggling to escape. 



In Chlamydoselachus the peculiar structure of the gill'covers is so conspicuous as to 

 form one of the most distinctive characters of the animal. The resemblance of the opercu- 

 lar fold to a short cloak or mantle suggested to Garman the generic name Chlaynydoselachus 

 of which the common name "cloaked shark" or "frilled shark" is a free translation. The 

 dorsal portion of each gill-flap is thrown into a projecting fold which is particularly con' 

 spicuous in the first pair. Presumably this is to allow for a large expansion when the 

 mouth is open and a large volume of water is passing through. These folds can be seen 

 on all the figures of the fish in this paper. However, they are particularly well shown in 

 Text-figures 7, 8, and 11; in Figures 6 and 

 7, plate II; and in Figure 16, plate V. 



Correlated with these gill-flaps in the 

 feeding-respiratory activities of the frilled 

 shark is the curious crescentic maxillary 

 fold, which as we have suggested (page 

 269) may function as a breathing-valve. 

 When the mouth is partly closed on prey 

 merely "nipped" by the outer front teeth, 

 the breathing-valve perhaps helps to pre- 

 vent the regurgitation of water during the 

 process of expulsion of the water through 

 the wide-open gill-slits. 



Text-figure 11 



A side view of the head of Chlamydoselachus to show 



the position and length of the lower jaw, the position 



of the nostril and of the eye, and the position and 



form of the gill-covers. 



After Garman, 1885.2. 



THE TRUNK OF CHLAMYDOSELACHUS 



The trunk of Chlamydoselachus, or that part of the fish extending from the head 

 to the end of the body-cavity, is in many ways different from that of other sharks. Its 

 structures and their position and arrangement present a number of interesting variations 

 and include at least one organ not previously noted in other fishes — the tropeic folds 



GENERAL FORM 



The absence of an anterior dorsal fin, together with the bunching of the single dorsal, 

 the anal, and the pelvic fins behind the middle portion of the body as a whole and in close 

 contiguity to the caudal fin, gives the fish a somewhat three-tailed appearance when 

 viewed from the side, and leaves the body proper entirely unobstructed almost from head to 

 vent. Garman (1885.1, p. 1) says of his 1511-mm. (59.5-inch) specimen (Text-figure 1) 

 that for a distance of almost two feet the body was entirely unrelieved by fins. This is 

 better shown in Garman's drawing reproduced as our Figure 16, plate V. In CoUett's 



