THE ANATOMY OF THE THYROID GLAND 163 



Mention is not made of the lateral nor of all the coronary arteries. 

 Parker's observations were made on Mustelus antarcticus. I 

 have dissected three species of the Selachii and one of the Batoidei, 

 I have not only been unable to confirm the course of the circulation 

 as indicated but I find that beyond the so-called hypobranchial 

 artery the course of the circulation is in the opposite direction, viz., 

 from the efferent branchial loops to the coronary vessels and 

 systemic capillaries, and the hypobranchial artery serves as a 

 relatively unimportant anastomosis which, in these species is not 

 even constantly present. In addition to the pair of coronary 

 arteries distributed to the ventricle I have in my specimens 

 observed a dorsal artery which ramifies largely in the wall of 

 the auricle. The mandibular artery as described and figured by 

 Parker, is the one from which in my preparations the thyroid 

 artery is sometimes, though not constantly, derived. His descrip- 

 tion leaves one somewhat in doubt as to the origin of this vessel, 

 but he has figured it correctly as coming from the first efferent 

 branchial loop. His coraco-mandibular artery, derived from 

 the mandibular, is a vessel which apparently corresponds with that 

 which distributes its main branches, in my preparations, within 

 the thyroid gland and only incidentally gives small branches to 

 the coraco-mandibular and coraco-hyoid muscles; T have there- 

 fore called this vessel the thyroid artery. 



G. H. Parker and Davis ('99) in an article on ''the blood-vessels 

 of the heart in Carcharias, Raia, and Amia" repeated the work of 

 Hyrtl ('58 and '72) so far as it immediately concerned the origin 

 of the coronary vessels, but being concerned only with the cardiac 

 vessels they made no mention of the thyroid artery or other deriva- 

 tives of the first hemibranch, nor of the gastric and pharyngeal 

 branches which arise in close relation to the anterior coronaries. 

 They described "the irregular longitudinal artery by which the 

 ventral ends of some or all of the efferent branchial arteries of a 

 given side are brought into communication, "hitherto referred to as 

 "longitudinal commissural" vessels (T. J. Parker) or as part of the 

 Arteria cardio-cardiaca (Hyrtl), and called the vessels the "lateral 

 hypobranchial artery, "reserving for the name commissural "those 

 arteries which leave the lateral hypobranchials on their median 



