100 BULLETIN OF THE BUREAU OF FISHERIES. 



greater portion of the brain, while the latter run caudad, on the ventral surface of 

 the medulla, to reach the spinal cord. On the sides of the lobi inferiors the posterior 

 cerebral arteries usually give off several small branches, one or two of which supply 

 the ear. 



In some teleosts (Opsanus and Limanda, tigs. 10 and 11) the internal carotids 

 join near their points of origin to form an arteria carotis interna impar; in others 

 (Leptocephahis, tig. '2) union does not take place until thej' reach the base of the 

 brain. The position and constant occurrence of the arteria carotis impar of teleosts 

 suggests its homology with the cranial end of the primitive dorsal aorta (Ayres, 

 1889) of the lower elasmobranchs. 



Tin second efferent branchial artery (tig. 16, pi. i. and tig. 12). About 2 cm. 

 from its ventral end the second efferent branchial artery (u) gives off a large branch 

 (38) corresponding to the fourth" commissural artery of Am in as described by 

 Parker and Davis (1899). This vessel (38) runs toward the median line and joins 

 its fellow of the opposite side at a point ventral to the thyroid gland and ventral 

 aorta, forming the median hypobranchial artery (/.'), which runs caudad, passing 

 below the ventral ends of the clavicles, and terminates in branches which supply the 

 ventral fins. 



The fourth commissural artery gives off three small branches, namely, two 

 nutrient arteries, one to the second (3.9) and one to the third (4-0) branchial arch, and 

 a ventral coronary artery (4-1), which is given off near the median line or, in some 

 cases, from the median hypobranchial artery itself, which runs caudad on the ventral 

 aorta and, in combination with a coronaiy artery that usually arises from the fifth 

 commissural artery, supplies the bulbus arteriosus and the heart. 



The median hypobranchial artery divides into the thyroid artery ( /•/), which 

 immediately enters the thyroid gland; two small branches (44) which supply part of 

 the m. sternohyoideus; and finally a branch (43) which supplies the muscles attached 

 to the clavicles. Opposite the cranial end of the basipterygium the coracoid artery 

 (SO) anastomoses, by means of a small branch, with the median hypobranchial. which 

 terminates (4.6) in the ventral tin. Since the coracoid artery is a branch of the. sub- 

 clavian, it will be described in connection with that artery. In teleosts where the 

 ventral tins are wanting (Leptocephalus and Spheroides, tigs. -J and 7), or where they 

 are situated far back on the abdomen (Pomolobus 6 , tig. 3), the median hypobranchial 

 artery is somewhat reduced in size and terminates in the m. sternohyoideus. Parker 

 and Davis (1899) have described it as dividing into coronary and epigastric branches, 

 but in many teleosts this description will not hold, for the coronary may be a branch 

 of the commissural artery. For this reason the entire median vessel formed by the 

 joining of the commissural arteries is designated in this paper as the median 

 hypobranchial artery. 



77/r third efferent branchial artery (tig. 1<>. pi. i. and tig. 12). Like the second 

 of the series, the third efferent branchial artery usually has but one branch, which 

 corresponds to the fifth commissural artery of Parker and Davis. This branch (/i) 



o Parker and ]>:i\ i>- in numbering the visceral arches followed the scheme laid down by Gegenbauer (1898), in 

 which the first visceral arch is represented bj the upper and lower jaws, the second by the hyoid arch, the third bj 

 the firsl branchial arch, etc. 



Mn Pomolobus the ventral lins arc supplied by a pair of somewhat larger peritonea] branches. 



