152 



ZOOLOGY 



SEf'T. XIII 



Fig. SIO.— Hemiscyllium, pelvic arch and 

 pelvic fin. imJa. uietapterygium ; ^jrfr. 

 liclvic ai-ch. 



bears only one large ray; the other two boar twelve or more 

 rays, differently arranged in the two genera. 



The pelvic /in (Fig. 816) has only a single basal cartilage (meta.) 

 articulating with the jidvic arch, with which also one or two of the 



fin-rays articulate directly. The 

 ^'■^^ pelvic arch (pelv.) is a nearly 



straight bar of cartilage which 

 runs transversely across the 

 ventral surface of the body, just 

 in front of the cloacal opening. 

 Enteric Canal (Fig. 817). — 

 The mouth leads into a very 

 wide cavity, the p)karynx, into 

 which open at the sides the in- 

 ternal apertures of the branchial 

 clefts and of the spiracle. From 

 this runs backwards a short 

 wide tube — the cesophagus (ces.) 

 — which passes behind into the 

 stomach. The domach is a 

 U-shaped organ, with a long 

 left limb continuous with the 

 oesophagus, and a short right 

 j)assing into the intestine. At the jnjiorus (p>yl.)~the point 

 where the stomach passes into the intestine — is a slight con- 

 striction, followed by a thickening. The intestine consists of two 

 parts— s?»rt// intestine or (luodeomm, and large intestine. The 

 former is very short, only an inch or two in length. The latter is 

 longer and very wide ; it is divisible into two portions— the colon 

 {cot.) in front and the rectn.m {rcct.) behind. The former is very 

 wide and is characterised by the presence in its interior of a spiral 

 valve, a fold of the mucous membrane which runs spirally round 

 its interior, and both retards the too rapid passage of the food and 

 affords a more extensive surflxce for absorption. The rectum 

 differs from the colon in being narrower and in the absence of the 

 spiral valve ; it opens behind into the cloaca. ^ 



There is a large liver (liv.) consisting of t>vo elongated lobes. A 

 roumhd s^c— the gall-hladder (g. />/.)— lie/ embedded in the left 

 lobe at its anterior end. The duct of the liver— the hilc-cluct {h. dct:) 

 —runs from the liver to the intestine. Proximally it is connected 

 with the gall-bladder, and by branch-ducts with the right and 

 left lobes of the liver. It opens into the commencement of 

 the colon. 

 _ Theimncreas (pancr.) is a light- cohjured compressed gland con- 

 sisting of two main lobes with a broad connecting isthmus, lying in 

 the angle between the right-hand limb of the stomach and the 

 small intestine. Its duct enters the wall of the small intestine 



