164 JEREMIAH S. FERGUSON 



sides and, after more or less tortuous courses, unite with one 

 another in the median plane" to produce by their union the median 

 hypobranchial artery. The ventral continuation of the subclavian 

 artery they call the "coracoid artery." Concerning the anasto- 

 mosis of this vessel with the median hypobranchial formed by the 

 hypobranchial artery of T. J. Parker they speak as follows: 

 "Moreover neither of these vessels [median and lateral hypobran- 

 chial] can be properly considered a dependency of the subclavian, 

 for the branch which leaves that artery, and which T. J. Parker 

 regarded as their root, may be connected with them, as Hyrtl 

 ('58, p. 17, Taf. 2) has shown, by only a relatively small vessel. 

 The union, then, is not in the nature of a continuous trunk, but an 

 anastomosis, and the vessel posterior to this union must be con- 

 sidered in the light of an independent artery. This we have called 

 the coracoid artery." 



MATERIAL AND METHODS 



For the purposes of the present study I have dissected 32 speci- 

 mens of Mustelus canis, 10 of Carcharias litoralis, 3 ofSqualus 

 acanthias, and 14 of Raia erinacea. In addition to these I have 

 had access to a number of sections from various Elasmobranchs 

 prepared by my late assistant. Dr. Guy D. Lombard. The most 

 of these animals were dissected through the courtesy of The Wis- 

 tar Institute of Anatomy at the Marine Biological Laboratory at 

 Wood's Hole, Massachusetts. My thanks are due these institu- 

 tions for the opportunity afforded. 



The form and position of the thyroid gland was carefully observed 

 in each instance and its vascular connections determined bothby 

 dissection and by various methods of injection. The injections 

 were made chiefly with a hypodermic needle of very fine caliber, 

 though finely drawn-out glass tubes were used with some success. 

 For pressure an aspirating syringe was used for routine work and 

 served very well; air pressure was also used at times. For tracing 

 the lymphatics, injections were frequently made into the substance 

 of the thyroid gland and into the connective tissue about the thy- 

 roid blood sinus and the other cervical blood vessels. For tracing 



