NOTIDANi 



139 



attachment of the jaws is more or less amphistylic, the branchial 

 slits are six or seven in number, and there is only one dorsal fin. 

 In the second group, the jaws are attached in modern forms on the 



Diagram of the branchial circulation of an Elasmobranch fish (modified from T. J. I'arker). 

 /'.'i, median anterior prolongation of aorta; n,.r, anterior carotid, efferent v.-ssel of spiracular 

 -ill (pseudobranch) ; n.ef, efferent vessel from last hemibranch ; ./, anterior efferent vessel ; 

 a/--8, live afferent vessels from ventral aorta ; a/.ci, afferent artery of spiracular gill : <:, conns 

 leading to ventral aorta ; </, coeliac artery ; d, ductus Cuvieri ; d.a, dorsal aorta ; </, epi branchial 

 artery; //.". hvnid efferent vessel; hp, hepatic veins; lit. heait; />.c, posterior eurotid ; ;>.'/, 

 l>osteri">r efferent vessel ; s, spiracle: c., ventral artery ; I-V, branchial slits. 



hyostylic plan, there are not more than live branchial slits (with one 

 exception, p. 152), and there are two dorsal fins (Miiller u. Henle 



D 



Diagram showing the principal modifications in tlx- arrangenifiit of the hyoid arch in th 

 Si lachii. (After Gegenbaur, from Sedgwick's Zwlogy.) A, in Htptaildnu ; B, in a shark ; 

 C', in Torpedo; D, in Rnj. llm, hyornandibular ; Ini, lower part of hyoid arch; ;>, prwcss 

 support ing .jaw --articulation ; r, branchial rays. 



[308], A. 8. Woodward [505], Dunu-ril [124], Regan [346], Jaekel 

 [238], etc.). 



GROUP I. 



Sub-Order 1. NOTIDANI. 



These sharks have a skull and jaw apparatus built on the 

 amphistylic plan. In Heptanchus, the palato-quadrate is firmly 



