Pseudobrauchial and Carotid Arteries in the Gnathostome Fishes. 109 



beyoncl that point being a part of the internal carotid proloni^ation 

 of the dorsal aorta. From the eiferent mandibular part of the artery 

 the ophthalmica magna arises. 



The hyoidean aortic arch is represented by the afferent and 

 efferent hyoidean arteries of Parker's descriptions, and then, dorsal 

 to the commissure that connects the efferent hyoidean and glosso- 

 pharyngeal arteries, by that part of Parker's posterior carotid 

 artery that extends from its origin up the point marked x by him. 

 There the efferent hyoidean artery joins the dorsal aorta; the vessels 

 y and ^ of Parker's descriptions representing the greatly reduced 

 hyoideo-glossopharyngeal section of the aorta. Parker wrongly 

 included the vessel y in the efferent hyoidean artery, the dorsal 

 aorta, according to him, terminating anteriorly in the vessel s. 

 Anterior to the point x, the dorsal aorta first includes a short 

 section of Parker's posterior carotid. Then the external carotid is 

 given off, represented in the terminal portion of Parker's posterior 

 carotid, and the aorta is continued onward in one half of each of 

 Parker's two vessels w; these two vessels not primarilj^ crossing in 

 the middle line, as Parker shows them, but simply anastomosing 

 there. Beyond the point where the vessel iv joins Parker's anterior 

 carotid, the so-called terminal portion of the latter artery represents 

 the premandibular portion of the aorta. 



In Selache maxima, the vessels are strictly similar to those in 

 Mustelus, although, as described by Carazzi (1905), they would 

 appear to be quite different. In Carazzi's figs. 16 and 17 it is 

 evident that the posterior carotid up to the point where it is 

 joined by the so-called vertebral artery is, as in Mustehis, simply 

 the dorsal part of the efferent hyoidean artery, the vertebral artery 

 and Carazzi's median vessel a forming the hyoideo-glossopharyngeal 

 section of the aorta. The aorta is then continued forward in a 

 short section of Carazzi's posterior carotid, and then in what Carazzi 

 describes as the smaller one of two branches into which that artery 

 sepamtes; this smaller branch anastomosing with its fellow of the 

 opposite side at the point c. The larger, or orbital branch of the 

 posterior carotid is the external carotid of my nomenclature, and 

 it is said to separate into three branches, on the smallest one of 

 which a small glomus (gomitolo) is said to form. From this glomus, 

 formed on a branch of the posterior (external) carotid, two branches 

 are said to arise, one of which Carazzi considers to be the arteria 

 ophthalmica magna; this artery thus being said to here arise from 



