The J^atural History of the Frilled Shar}{ 285 



huge liver becomes enlarged at times and may then obliterate the ridges and groove — i.e., 

 that they are a sort of "expansion-joint'' structure. This does not appeal to us since no shark, 

 much less this one, is known to have such periodic volumetric changes in the liver. On 

 the whole it seems possible that the tropeic folds may have somewhat the same function 

 as the keel of a ship. 



CLOACAL APERTURE AND ABDOMINAL PORES 



The cloacal aperture is situated between the posteriorly placed pelvic fins, hence 

 it is posterior to the center of the body as a whole. This aperture in the male fish is 

 portrayed in Giinther's drawing (our Figure 17, plate V) as an elliptical opening. In our 

 embryos it consists of a longitudinal slit with somewhat turgid lips. The abdominal pores, 

 a pair of canals leading from the abdominal cavity to the exterior, open on each side of the 

 hinder part of the aperture, each at the summit of a small elevation. In our three adult 

 females we find the abdominal pores in the same place as in our embryos. Each pore is 

 protected on the side by the pelvic fin, and behind by a fold of integument extending from 

 the base of the fins to the ventral surface of the body. 



Carman's drawing (1885.2) of the abdominal pores in external view in a female is 

 reproduced herein as Figure 18, plate V. Here, judging by our specimens, the pores are 

 entirely too large. Furthermore, they are shown embedded in a common mass of tissue 

 and in the hinder part of the cloacal aperture, whereas in our specimens they are always 

 separate and situated on the lips of the cloacal aperture in front of its hinder edge. In 

 another plate (his No. XII) Carman (1885.2) figures a dissection of the pelvic fins, cloaca, 

 and abdominal pores of his first specimen. Here these pores are situated one on the 

 hinder part of each side-wall of the cloacal opening. 



In the matter of the position of the abdominal pores with reference to the cloacal 

 aperture, we find considerable variation. The position of the pores on Carman's fish 

 and on our three is, we beUeve, the normal one. Ciinther (1887), in his Fig. 1, pi. LXV, 

 shows the pores as paired papillae placed behind the hinder rim of the cloacal aperture. 

 A closely similar condition is found in Doctor White's 

 specimen. 



Still greater variations, amounting to undoubted 

 abnormalities, are now to be reported. Ciinther, in 

 one of his male fish from Yeddo Bay, found but one ab' 

 dominal pore, that on the left side. Furthermore, it was 

 outside of and behind the cloacal aperture. No state- 

 ment was made as to his third specimen (a female). In 

 our fish No. 1 there are two papillate structures on the 

 side-walls of the cloacal opening just anterior to its 



hinder end. That on the right is plainly a normal ^, . , /^ . !^"'^^ , , r 



° 1 1 1 r J • 1 The dermal denticles at the angle ot 



abdominal pore, but no opening could be found in the ^^^ ^^^^^^ (^5) ^^^^ ^^^ f^.^^ ^^, 



left papilla. These structures may be made out clearly semblance to the form of the teeth, 

 in our Figure 19, plate V. These openings, together with After Garman, 1885.2. 



