108 EDWARD PHELPS ALLIS, JR. 



the mandibula, and, from its course and distribution, is unques- 

 tionably the mandibular artery (arteria mandibularis) , not only 

 of Parker's descriptions of the adult Mustelus antarc.ticus, but 

 also of the similarly named artery in Carazzi's ('05) descriptions 

 of the several selachians examined by him. It will accordingly 

 be so called for the present, although it will be later shown that 

 it is the anterior efferent artery of the hyal arch. 



Having given off these two branches, the lateral hypobranchial 

 artery continues anteriorly, internal to the musculus interman- 

 dibularis, and, opposite the thyreoid gland on one side of the 

 head of my specimen (but slightly anterior to that gland on the 

 other), sends a branch forward internal to the mandibula. The* 

 artery itself then turns outward around the ventral edge of the 

 mandibula, and, piercing the musculus intermandibularis near 

 its lateral edge, reaches the external, ventro-lateral surface of 

 the mandibula. The branch sent forward internal to the man- 

 dibula lies internal to the musculus intermandibularis, and is the 

 submental artery of Parker's descriptions of Mustelus antarcticus. 

 Slightly posterior to the symphysis of the mandibles it unites, 

 in the median line, with its fellow of the opposite side, and a 

 small median branch is sent posteriorly and a somewhat larger one 

 anteriorly. From this latter artery, at the symphysis, a branch 

 is sent postero-laterally, on either side, along the internal surface 

 of the mandibula, near its ventral edge, and is lost in a mass of 

 tissue which looks like degenerate glandular tissue. 



The submental artery, although it actually runs anteriorly, is 

 morphologically a ventral branch of the lateral hypobranchial 

 artery directed toward the distal end of the mandibula. It is 

 accordingly a serial homologue of the more posterior ventral 

 branches of the lateral hypobranchial artery, one of which 

 branches goes to the thyreoid gland while others unite in the 

 median line to form the median hypobranchial and coronary 

 arteries (Allis, '11 b). 



The lateral hypobranchial artery, having reached the ventro- 

 lateral surface of the mandibula, sends a delicate branch dorso- 

 posteriorly, immediately lateral to the lateral edge of the mus- 

 culus intermandibularis and, itself continuing onward, falls 



