ALIMENTARY SYSTEM. 



5°5 



■PC.V 



The eyes are large but lidless ; the small nasal sacs with 

 plaited walls have double anterior 

 apertures ; the vestibule of the ear 

 contains a large solid otolith, and 

 another very small one in a pos- 

 terior chamber. The dark lateral 

 line, covered over by modified 

 scales, lodges sensory cells, and is 

 innervated by a branch of the vagus. 

 Alimentary system. — Teeth are 

 borne by the premaxillae, the vomer, 

 and the superior pharyngeal bones 

 above, by the dentaries and the in- 

 ferior pharyngeal bones beneath. 

 There are no salivary glands, no 

 spiracles, nor posterior nares. A 

 small non-muscular tongue is sup- 

 ported by a ventral part of the 

 hyoid arch. Five gill-clefts open 

 from the pharynx ; their inner mar- 

 gins are fringed by horny gill rakers 

 attached to the branchial arches 

 and serving as strainers ; they pre- 

 vent the food from being swept out 

 with the respiratory current. The 

 gullet leads into a curved stomach ; 

 at the junction of stomach and 

 duodenum numerous tubular py- 

 loric caeca are given off; into the 

 duodenum opens the bile-duct from 

 the gall-bladder and liver ; the coiled 

 intestine passes gradually into the 

 rectum, which has an aperture 

 apart from those of the genital 

 and urinary ducts. There is no 

 spiral valve, and there are no ab- 

 dominal pores. A pancreas is ab- 

 sent ; perhaps the pyloric ca?ca take 

 its place. The peritoneal mem- 

 brane which lines the abdominal cavity is darkly pigmented. 

 Respiratory system. — Water that passes in by the mouth 



Fig. 218. — Diagram of Tele- 

 ostean circulation. — After 

 Nuhn. 



A., auricle; V., ventricle; b.a., 

 bulbus arteriosus; v.a., ventral 

 aorta ; a.br., afferent bran- 

 chials ; e.br., efferent bran- 

 chials ; c.c. y cephalic circle ; 

 e. , carotids; A.c.v., anterior 

 cardinal veins; P.C.V., pos- 

 terior cardinal veins; d.c, 

 ductus Cuvierii ; d.a., dorsal 

 aorta; c.v., caudal vein ; c.a., 

 caudal artery ; A'., kidney. 



