INTESTINE. 129 



valve, close to which the ductus choledochus enters, indicating 



Fig. 55. — Siphonal stomach and spiral valve of Basking-Shark (Selache). 

 (After Home and Owen.) 

 It, CEsophagns ; J, Cardiac portion of stomach ; c, pyloric portion ; d, ponch in- 

 termediate between stomach and duodenum, with circular valves at both 

 ends J e, Duodenum ; /, Valve of intestine ; g, Ductus hepaticus ; h, Spleen. 



the boundary of the iatestine proper (Fig. 57, p). The spiral 

 valve is perfect, and makes from three {Chimcera) to niae 

 {Geratodus) gyrations. A cloaca is present, as in Chon- 

 dropterygians. A mesentery fixiag the dorsal side of the 

 intestine is absent. 



The other Ganoids resemble again more the Chondrop- 

 terygians in the structure of their intestinal tract. The 

 stomach has always a distinct pyloric portion, and has a still 

 more compKcated structure iu Acipenser. The duodenal 

 portion receives the contents of Appendices pyloricce, which 

 are confluent into a gland-like mass in Acipenser, but separate 

 ia Polyodon, and numerous and short in Lepidosteus, whilst 

 Folypterus possesses one such appendage only. A spiral 

 valve is developed in the Sturgeons and Polypterus, but in 

 Amia, in which the intestine performs several convolutions, 



