584 



arteries. It accordingly is quite certain that my diagrammatic figure 

 represents the true condition of these vessels, and that this condition 

 is derived from an arrangement of these vessels such as is shown by 

 HocHSTETTER in a figure of a 17 mm embryo of Acanthias vulgaris 

 (1906, Fig. 98), and not from that shown by Dohrn in Scyllium and 

 Pristiurus ; this condition of these vessels in this embryo of Acanthias 

 persisting even in the adult (Hyrtl, 1872). And it should be noted 

 that the term "first aortal root", as used by Raffaele, is misleading 

 and not strictly correct, for this root, which varies greatly in compo- 

 sition in different elasmobranchs, must, whatever its composition, and 

 even where it is formed wholly by a part of the hyoideo-glossopharyn- 



ef a.cer pxer 



'Ifi aal elh ra cor 



Fig. 1. Lateral view of the branchial, pseudobrauchial and carotid arteries in 

 Raja radiata, the dorsal artery swung upward and appearing as in dorsal view. — 

 aal^ 11^ etc. afferent arteries in the 1st, 2nd, etc. branchial arches ; a.cer anterior 

 cerebral artery ; ahy afferent hyoidean artery ; amd afferent mandibular artery ; 

 apsb afferent pseudo branchial artery ; cc common carotid artery ; ch choroid gland ; 

 cor coronary artery ; da dorsal aorta ; ea J, JZ, etc. efferent arteries in the 1st, 

 2nd, etc. branchial arches ; ec external carotid ; ehy efferent hyoidean arteiy ; 

 epsb efferent pseudobranchial artery ; ic internal carotid ; ihl internal lateral hypo- 

 branchial ; Ida lateral dorsal aorta ; om ophthalmica magna artery ; op optic artery ; 

 p.cer posterior cerebral artery ; psb pseudobranch ; s.ahy secondary afferent hyoidean 

 artery ; ta tnincus arteriosus. 



geus section of the lateral dorsal aorta, as in Heptanchus and Chlamy- 

 doselachus, fall directly into the median dorsal aorta. 



Returning now to Raja radiata, the circulus cephalicus of this 

 fish, anterior to the posterior section just above considered, is continued 



