152 



ZOOLOGY 



SECT. XIII 



FIG. 816. Hemiscyllium, pelvic arch and 



pelvic fin. 

 pelvic arch. 



mtta. metapterygium ; pelr. 



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

 rays, differently arranged in the two genera. 



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

 articulating with the 2^lvic arch, with which also one or two of the 



fin-rays articulate directly. The 



pelv 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 pharynx, 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 esophagus (ces.) 

 which passes behind into the 

 stomach. The stomach is a 

 U-shaped organ, with a long 

 left limb continuous with the 

 oesophagus, and a short right 



passing into the intestine. At the pylorus (pyl.) the point 

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

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

 parts small intestine or duodenum, 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' 

 (ccL) in front and the rectum (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 surface 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 two elongated lobes. A 

 rounded sac the gall-Uadder (g. U.) lies embedded in the left 

 lobe at its anterior end. The duct of the liver the lile-duct (b. 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. 



The pancreas (pancr) is a light-coloured 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 



