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TEXTBOOK OF ZOOLOGY 



The pectoral girdle is composed of the ventral coracoid bar and 

 the dorsolateral scapular process at each end of it. The fin consists 

 of three flat basal cartilages (propterygimn, mesopterygimn, and 

 metapteryginm), a series of radial cartilaginous rays, and a series of 

 exoskeletal dermal rays. The pelvic girdle is made of one cartilagi- 

 nous bar (ischiopubis) with a fin joining at each end. The basals of 

 this fin are fused into one cartilaginous plate. 



Fig. 232, A. — Dissection of the valvular portion of the small intestine. A, the 

 bonnet-head shark to show the spiral valve; B, spiral valve of Raia. (B re- 

 produced by permission, from General Zoology by Wieman, copyrighted 1938 by 

 McGraw-Hill Book Co., Inc.) 



Digestive System 



Most of the organs of this system and other viscera lie in the 

 pleuroperitoneal portion of the coelomic cavity. Anterior to this the 

 pericardial portion of the coelom contains the heart. The digestive 

 organs are in the form of an alimentary canal with accessory glands. 



