THE ELASMOBRANCH FISHES 



163 



branchial artery {l.hb., fig. 153); or the lateral liypobranchial vessels may 

 arise from tlie ventral parts of the eiferent-colleetor loops; or again a lateral 

 hypobranchial segment may be incomplete between certain of the commis- 

 surals. Jnst before reaching the midventral line the commissurals of each side 

 form a larger longitudinal vessel, the median hypobranchial {m.Jib.),i\i.e right 

 and left median hypobranchials being connected by several small connectives 

 {en.) which may or may not unite right and left pairs of commissurals. The 

 tAvo median hypobranchial trunks are continued posteriorly above the peri- 



Fig. 152. Arterial branches of first efferent-collector, Heptanchus macuJatus. (Marie Weldt, 

 orig.) 



a.c, anterior cerebral ; a.sp., arteria spinalis ; hr.ef}, first branchial efferent; d.a}, paired 

 dorsal aorta; d.a., dorsal aorta; hy.ef., hyoidean efferent; i.e., internal carotid; m.c, median 

 cerebral; ns., nasal artery; o.vi., ophthalmica magna; or., orbital artery; p.c, posterior 

 cerebral; ps., pseudobranchial artery; r.a., ramus anastomoticus ; rs., rostral artery; sg., 

 segmental artery. 



cardial roof as the two large pericardial arteries (^^c). The pericardials may 

 be of essentially the same size or the right one may be the better developed 

 (see fig. 154, r.pc). The epigastric artery (epg., fig. 154), which supplies 

 branches to the oesophagus and the stomach, is a branch off of the pericardial 

 or is the direct continuation of the right one. 



A large vessel is given off from the median hypobranchial between commis- 

 sures two and three, or three and four, which passes to the midventral line and 

 joins a similar artery from the opposite side. This united trunk extends poste- 

 riorly, and at the sixth commissural divides into the right and left coracoid 

 arteries (co.a.), which join the subclavian arteries. Similarly, near the sixth 

 commissural, an artery arises from the median hypobranchial on each side to 

 pass posteriorly and toward the midventral line. This artery, however, does 

 not reach or fuse with its fellow from the opposite side, but continues as the 

 coronary artery (cr.L, figs. 153 and 150) to the heart. 



In Heptanchus maculatus the left coronary (cr.l., fig. 150a) runs along the 

 dorsal and left side of the conus arteriosus, supi^lying it and the dorsal side of 



