96 BULLETIN OF THE BUREAU OF FISHERIES. 



directly dorsal to the parasphenoid. From this point it continues dorsad and craniad 

 between the rectus inferior and rectus posterior and pierces the sclerotic at the 

 lower edge of the optic nerve. Within the eye it forms an anastomosis known as 

 the "choroid gland." 



According to Maurer the hyoidcan artery represents in teleosts the most anterior 

 of the six aortic arches, or the mandibular aortic arch. He states that in the trout 

 embryo two vessels are developed in connection with the hyoid arch, one of which is 

 situated in front of and the other behind the cartilage. The former is regarded by 

 him as equivalent to the mandibular aortic arch, the latter as equivalent to the hyoid- 

 can aortic arch. Since the vessel in front of the cartilage alone persists in the, adult, 

 becoming the hyoidean artery, it is the homologue of the mandibular aortic arch. 

 Both of these vessels are originally connected with the anterior end of the ventral 

 aorta, their connection with the first efferent branchial artery, which is characteristic 

 of the adult, being a secondary one (Maurer, 1888). Allis (1901) also seems to regard 

 the hyoidcan artery as belonging to the mandibular rather than the hyoid arch. He 

 savs (o]). cit., pp. 115-116), "This postero-ventral prolongation of the efferent pseudo- 

 branchial arten of 12 mm. larva' of Amia thus has, in its dorsal portion, the same 

 relation to the cartilage of the palato-quadrate arch that the branchial arteries have 

 to the cartilages of their respective arches. * * In its ventral portion this 



artery acquires relations to the hyoid arch, but it there lies anterior to the cartilage 

 of the arch and not posterior to it. * * * It thus has a position it could naturally 

 acquire by simply slipping backward oil the hind edge of the mandibular cartilages. 

 * * * In both its ventral and dorsal positions this artery seems to correspond 

 closely, in general position, to the artery usually described in teleosts as the arteria 

 byoidea." 



Wright (1885) regards the hyoidcan artery as representing simply the enlarged 

 nutritive branch to the hyoid arch. He says (op. cit.. p. 486): ■"The condition of 

 the parts in Lepidostexut proves that the arteria hyoidea of the teleosts is not the 

 homologue of the hyoidcan aortic arch, a-- is sometimes assumed, for the two vessels 

 coexist in the genus. * * * It appears to me to be homodynamous with the 

 nutritive or branchial arteries which spring from the succeeding efferent arteries, in 

 the way this does from the first, and to owe its greater relative size in ganoids and 

 teleosts to the development of the gill cover from the hyoid arch." 



Owen (1866) arid others, however, regard the hyoidean artery as equivalent to 

 the hyoidean aortic arch. From the conditions found in the adult teleost, the writer 

 can see no reason for assigning it to the mandibular rather than to the hyoid arch. 

 It seems perfectly natural to regard it as belonging to the latter, and as representing 

 the more cranial of the two efferent vessels which are present on each branchial arch 

 in sharks and rays. 



( '. Tin next branch of lh< first efferent branchial artery is a small ex*, I (ll) 

 which arises near the dorsal end of the first gill, and. passing caudad, dorsal to the 

 second and ventral to the third branchial artery, supplies the muscles and membranes 

 at- the dorsal ends of the gill arches. 



D. The carotid nrt<ri<* ami their branches (tig. 16, pi. i). The carotid artery 

 ( 16) is given off at the angle where the first efferent branchial artery bends caudad to 

 join the second. Almost immediately beyond its origin it sends off a large branch, 



