120 Edward Phelps Allis jr., 



and the internal carotid, is not found in any adult teleost; Virchow 

 (1889) making the same statement. Dohen then further says tliat 

 this portion of the mandibular aortic arch is found in very young 

 stages of teleostean embryos, exactly as it is in selachians; that it 

 first diminishes in relative importance; is then pinched off from the 

 internal (posterior) carotid; and then immediately goes to form a 

 small commissure extending from the ophthalmica magna of one side 

 to that of the other. While this may be so, it seems to me less 

 probable than the utilization of the vessel for an orbito-nasal; and^ 

 furthermore, Dohrn's figures are not strictly in accord with the 

 supposition he makes. In his fig. 1, for example, of the vessels in 

 a 11 mm trout embryo, the ophthalmica magna is shown arising 

 from the lateral aortic trunk some little distance anterior to the 

 point where that trunk is joined by the dorsal end of the efferent 

 pseudobranchial artery. Here, if the dorsal end of the latter artery 

 were to be pinched off from the aortic trunk (posterior carotid), as 

 DoHRN describes, it manifestly could not become a commissure 

 between the ophthalmicae magnae of opposite sides. 



HocHSTETTER (1906, p. 93) givcs a somewhat different account 

 of the formation of the commissure between the ophthalmicae magnae. 

 He says that the internal carotids are primarily independent of each 

 other, that they later become connected by cross-commissure in the 

 plane of the dorsal ends of the mandibular aortic arches, and that 

 still later this anastomosis is split up in such a way that the 

 ophthalmicae magnae become connected by cross-commissure, those 

 arteries at the same time losing their connection with the internal 

 carotids. 



The ophthalmic branch of the external carotid of Amia is 

 apparently represented in the Loricati by the sclerotic-iris artery 

 of Allen's descriptions. One branch of this artery enters the 

 cranial cavity and becomes the anterior cerebral artery, a second 

 branch, according to Allen, entering the "skull" to reissue as the 

 iris artery; this latter artery however probably simply traversing 

 a chamber in the skull wall, and not entering the cranial cavity 

 at all. 



The arteria hyoidea, or afferent pseudobranchial artery, is shown 

 in my diagram as the mandibular aortic arch, because of Dohrn's 

 statement (1886, p. 166), later confirmed by Maurer (1888, p. 20)^ 

 that it belongs to that arch and not to the hyoidean arch. 



In teleosts other than the Loricati, the pseudobranchial arteries 



