The Tiatural History of the Frilled Shar}{ 293 



position of the dorsal fin allows a more sinuous motion of the forepart of the body. Gar' 

 man (1885.2, p. 13) speaks thus of the ''comparatively small dorsal": 



This fin begins above the origin of the anal, as is indicated by the peculiar armature of 

 the upper edge, and gradually rises backward to terminate in an acute point about opposite 

 to a similar point on the anal fin. Both upper and lower (anterior and posterior) margins are 

 curves which meet in the apex. 



For illustrations showing this fin, as well as the anal and caudal fins now to be 

 described, see Text-figure 1 and Figures 1 and 2, plate I. The matter of the "arma- 

 ture" will be taken up later in considering the like structure on the dorsal edge of the 

 caudal fin. 



Anal Fin. — This fin, in most sharks a relatively small structure, is in Chlamydo' 

 selachus an unusually large one. Originating a short distance behind the cloaca and imme- 

 diately underneath the origin of the dorsal, its tip extends backward to the point of 

 origin of the ventral lobe of the caudal. Arising from a base unusually long for a shark, the 

 total length of this fin is about three times its depth. It has a smoothly rounded outline, 

 except that in some specimens an acute angle is formed by its posterior extremity. How- 

 ever, in two of our fish this point is rounded. This fin is well shown in Carman's draw- 

 ing (our Figure 16, plate V) and in Gunther's lithographed figure (our Figure 1, plate I). 

 From the si2;e of the anal fin, we judge that it is of considerable use in locomotion. 



Caudal Fin. — In sharks this fin includes the hinder portion of the tail. In Chlamy 

 doselachus the caudal fin is such a unique structure, and there is so much diversity in the 

 figures and descriptions of it, that it has been necessary to study it with much care. The 

 published figures and descriptions will be taken up in chronological order, and then our 

 own observations will be presented. 



Carman's first illustration (1884.1), shown in our Text-figure 1, portrays a tail-fin 

 having a gentle curve upward, with a rudimentary dorsal fin-lobe devoid of rays, and on 

 the ventral surface a large fin-lobe with many rays. His second and more finished drawing 

 (1885.2) shows these structures better (see our Figure 16, plate V). The tip of the tail 

 of this first specimen ends abruptly as if it had been bitten off. This, apparently, he did 

 not recognize until he examined his second fish, when he wrote a short note (1887, P- 267) 

 correcting his oversight. Here he says that the tail of his first specimen was "deformed 

 and incomplete; the deformity in all likelihood being of embryonic origin." The particu- 

 lar thing to which we wish to call attention here is that in both his figures the tail-fin is 

 bent upward shark-fashion. 



Giinther (1887) in our Figure 1, plate I, portrays the tail of Chlamydoselachus as a 

 long, slender, pointed organ, with a serrated dorsal edge, extending the line of the body 

 straight backward, but in its hinder half (which comprises the tail-fin) drooping slightly 

 below this line. The tail-fin has a rudimentary dorsal lobe. This fin-lobe begins under the 

 tip of the dorsal and increases gradually in height until well toward the end of the tail. 

 At the tip it becomes continuous with the ventral lobe of the caudal fin. In Cunther's 

 figure the dorsal lobe of the caudal fin has a serrated edge which might be interpreted as 



