210 



ZOOLOGY 



SECT. 



i 



l/m. 



are attached three partly ossified nodules, the distal pterygio- 

 phores (ptg), and with these the dermal fin-rays are articulated. 

 The adipose lobe of the pelvic fin is supported 

 by a small scale-like bone. 



The muscles of the trunk and tail are 

 arranged, as in the Dog-fish, in zigzag myo- 

 meres : there are small muscles for the fins, 

 and the head has a complex musculature for 

 the movement of the jaws, hyoid, operculum, 

 and branchial arches. 



The coelome is divisible into a large ab- 

 domen (Fig. 865) containing the chief viscera, 

 and a small 'pericardial cavity, situated below 

 the branchial arches, and containing the heart. 

 Digestive Organs. — The inotulli (Figs. 854 

 and 865) is very large and has numerous 

 small, recurved, conical teeth, borne as already 

 mentioned, on the premaxillse, maxillae, pala- 

 tines, vomer, dentaries and basihyal. They 

 obviously serve merely to prevent the escape 

 of the slippery animals used as- food and are 

 of no use for either rending or chewing. The 

 •pharynx {ph.) is perforated on each side by 

 four vertically elongated gill-slits, fringed by 

 the bony tooth-like gill-rakers. Each gill-slit 

 is V-shaped, the epihyal being bent upon 

 the ceratohyal so that the dorsal and ventral moieties of 

 the branchial arches touch one another when the moutli is 

 closed. 



The pharynx leads by a short gullet {gut) into a U-shaped 

 stomach (st.) consisting of a wide cardiac and a narrow pyloric 

 division : between the latter and the intestine is a ring-shaped 

 pyloric valve. The intestine passes at first forwards as the 

 duodenum (du.), then becomes bent upon itself (i7it.) and passes 

 backwards, without convolution, to the anus (an.). Its posterior 

 portion has the mucous membrane raised into prominent annular 

 ridges which simulate a spiral valve. 



The liver (Ir.) is imperfectly divided into right and left lobes, and 

 there is a large gall-bladder (g. hi.). Opening into the duodenum 

 are about forty blind glandular tubes, the pyloric cceca {py. c). 

 There is a large spleen (spl.) attached by peritoneum to the fundus 

 of the stomach. The stomach, duodenum, and pyloric caeca are 

 surrounded by loose folds of peritoneum loaded with fat. 



Lying below the kidneys and extending the whole length of the 

 abdominal cavity is the air-bladder (a.bl.), a thin-walled sac 

 serving as an organ of flotation. Anteriorly its ventral wall 

 presents a small aperture leading, by a short pjncuviatic duct 



Fig. 864.— Salmo fario. 



Skeleton of left pelvic 

 fin, dorsal aspect. 

 B. PTG. basiptery- 

 gium ; D. F. R. dermal 

 fill-rays ; PTG. distal 

 ptcrygiophores. 



