160 JEREMIAH S. FERGUSON 



pass backward to supply the anterior coronary vessels. Hyrtl 

 very clearly pointed out that the posterior coronary vessels 

 arise from the subclavian artery in the Batoidea and in 1872 he 

 showed that these vessels (posterior coronaries) were absent in the 

 Selachii, a point emphasized at considerable length some years 

 later by G. H. Parker and Davis ('99) . In 1872 Hyrtl extended his 

 description of the hypobranchial arterial system to the Selachii. 

 He found the thyroid gland to be supplied by the ''Arteria thy- 

 reo-maxillaris seu submentalis" which supplied the floor of the 

 mouth and thyroid gland as in the Batoidei but which took origin 

 from the ''veins" of the first gill sac, rather than from the second 

 as he had previously described for the Batoidei. He also described 

 the ''Arteria cardio-cardiaca," called later the "commissural" 

 and "longitudinal commissural" (T. J. Parker) and the commis- 

 sural and ''lateral hypobranchial" (G. H. Parker and Davis), 

 which fused in the median line to form a median vessel (median 

 hypobranchial) and from which the coronary vessels were derived. 

 At this time Hyrtl emphasized the absence of the posterior coro- 

 nary branches of the subclavian in the sharks and called attention to 

 an anastomosis from the subclavian forward to the median vessel 

 from which the coronary arteries arose. This anastomotic vessel 

 has since been called by T. J. Parker the "hypobranchial artery." 



Turner ('74) injected the conus arteriosus and studied the 

 course of the afferent and efferent branchial vessels; the course of 

 these vessels is now well known. He neither mentioned nor ex- 

 cluded any relation to the thyroid gland, apparently not recogniz- 

 ing this organ, nor did he work out the ultimate connections of 

 any of the smaller cervical vessels. 



T. J. Parker (*80) described the venous system of Raia nasuta 

 and called attention to "the extraordinary number of transverse 

 anastomoses it [the venous system of the skatej presents, the results 

 being to produce numerous 'venous circles, 'comparable to the circle 

 of Willis in the arteries of the mammalian brain, and the circulus 

 cephalicus in the arterial system of bony fishes. There is also 

 a direct passage from the sinus venosus and back again, in four 

 different ways, namely: (1) by the hepatic sinus; (2) by the an- 

 terior part of the cardinal vein and the cardinal sinus ; (3) by the 

 whole length of the cardinal veins and their posterior anastomosis ; 



