174 



THE ELASMOBRANCH FISHES 



collector which forms the anterior part of the loop, however, is a posterior 

 efferent-collector, for it drains the posterior demibranch of a whole gill ; and 

 the efferent-collector posterior to the cleft is the anterior efferent-collector of 

 the following gill. To make this clear, if the area between two pockets, for 

 example between the first and second pockets, be considered (fig. 161), its 

 anterior efferent-collector (the second) drains the demibranch just behind 



Fig. 162. Dorsal view of afferent and efferent arteries, Basyatis dipterura. (Blanche Lilli- 

 bridge, orig.) 



ac, accessory branchial arteries; hr.ef., branchial efferent arteries; c.tr., cross-trunk; ce., 

 coeliac axis; efc, efferent-collector; e.c, external carotid; hy.ef., hyoidean efferent; p.c, 

 posterior cerebral artery; ps., pseudobranchial artery; s.cl., subclavian artery; s.m., su- 

 perior mesenteric; I, first gill cleft. 



