xm 



PHYLUM CHORDATA 



147 



d.r 



coracoid portions are produced forwards in the middle line into a 

 flattened process supporting the floor of the pericardial cavity in 

 which the heart is 

 lodged. The three 

 basal cartilages of 

 the fin are named, 

 respectively, the 

 anterior, proptery- 

 gium (pro.), the 

 middle, mesoptery- 

 gium (meso.), and 

 the posterior, me 

 tapterygium (meta.). 

 Of these the first is 

 the smallest and the 

 last the largest : the 

 first bears only one 

 large ray ; the other 

 two bear twelve or 

 more rays, differ- 

 ently arranged in 

 the two genera. 

 The pelvic fin 



(.big. OZb) has Only FJQ 82 5._Hemiscyllium, pectoral arch and fin. d. r. dermal 

 a Single basal Car- horny rays ; meso. mesopterygium ; meta. metapterygium ; pect. 



tilage (meta.) articu- pectoral arch : * ro ' ter am - 



lating with the pelvic 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. 827). 

 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 oesophagus (OBS.) 

 which passes behind into the 

 stomach. The stomach is a \J- 

 shaped organ, with a long left 



limb continuous with the oesophagus, and a short right one 



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



K 2 



FIG. 826. Hemiscyllium, pelvic arch and 

 pelvic fln. meta. metapterygium ; pelv. 

 pelvic arch. 



