NOTIDANl 



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 



da. 



/it. 



Flo. 98. 



Diagram of the branchial circulation of an Elasmobranch fish (modified from T. J. Parker). 

 (i,.c, median anterior prolongation of aorta ; a.c, anterior carotid, efferent vessel of spiraeul.-ir 

 gill (pseiulobranch) ; a.ef, efferent vessel from last hemihranch ; ti.f, anterior efferent vessel ; 

 o/--6, five afferent vessels from ventral aorta ; af.n, afferent artery of spiracular gill ; c, conns 

 lending to ventral aorta ; d, coeliac artery ; d, ductus Cnvieri ; d.a, dorsal aorta ; /, epi branchial 

 artery ; f>.<>, liyoid efferent vessel ; lip, hepatic veins; lit, heart; />.<:, posterior carotid; p.rf, 

 posterior efferent vessel ; s, spiraclo ; J'., 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 (Mu'ller u. Henle 



FIG. 0'.' 



Diagram showing the principal modifications in the arrangement of the hyoid arch in the 

 Srlachii. (After Gegenbaur, from Sedgwick's Zoology.) A, in Htptanehv*; IJ, in a shark; 

 C, in Torpedo; D, in Rajo-. Hm, hyomandibular ; hit, lower part of hyoid arch; /, process 

 supporting jaw-articulation ; r, branchial rays. 



[308], A. S. Woodward [505], Dumeril [124], Regan [346], Jaekel 

 [238], etc.). 



GROUP J, 



Sub-Order 1. NOTIDANl. 



These sharks have a skull and jaw apparatus built on the 

 umphistylic plan. In Heptanchm, the palato-quadrate is firmly 



