116 EDWARD PHELPS ALLIS jr., 



hyoidea of Wright's descriptions of the fish. Of this artery Wright 

 says (9, p. 498) that it "does little more than supply blood to 

 the extremely large thyroid and certain other structures on the ventral 

 aspect". In both its ventral and its dorsal portions the artery seems 

 to correspond closely , in general position , to the artery usually de- 

 scribed in Teleosts as the arteria hyoidea, but to which Maurer (6) 

 has given the name arteria hyo-mandibularis. This artery is, however, 

 I believe, always said to perforate both the hypohyal and the hyo- 

 mandibular, neither of which are perforated by the artery of Amia. 

 The artery in these Teleosts thus has, in its dorsal portion, the 

 course of a venous vessel in Amia, that is described below, but this 

 may not be of importance, as in Scomber the artery passes anterior 

 to the hymandibular, as has been fully set forth in a work I have 

 now in press. The artery, in 12 mm embryos of Amia, is certainly 

 the afferent artery of the pseudobranch , and it is, at that age, the 

 only direct and continuous afferent vessel of the organ. As it arises, 

 in still younger embryos of Amia, from the ventral arterial trunk, 

 and not from the efferent artery of the first branchial arch, and as 

 it is replaced, in older larvae than 12 mm ones, by another and 

 totally different afferent artery, I shall, to prevent confusion, hereafter 

 refer to it as the primary afferent pseudobranchial artery. 



Associated with this primary afferent pseudobranchial artery, and 

 closely following it in the middle part of its course, there is, at this 

 age, a large venous vessel. Dorsally this venous vessel connects, 

 through the facial canal through the hyomandibular, with the large 

 venous vessel that lies along the dorsal surface of the adductor hyo- 

 mandibularis muscle, in the angle between the dorsal end of the hyo- 

 mandibular and the lateral surface of the skull. An anterior pro- 

 longation, or branch, of the vessel accompanies the primary afferent 

 pseudobranchial artery around the anterior edge of the hyomandibular 

 to the hind end of the pseudobranch and there disappears. 



In addition to the primary afferent pseudobranchial artery, above 

 described, there is, in Amia, another afferent vessel that certainly, in 

 12 mm larvae, transmits blood a large part of which, at least, is 

 destined to reach the pseudobranch and, beyond that organ, to tra- 

 verse the efferent pseudobranchial artery. This second afferent pseudo- 

 branchial current is not, however, a continuous one, being transmitted 

 by ventral and dorsal vessels separated by a capillary region. The 

 ventral vessel has already been referred to as the afferent artery to 

 the gill cover, an artery that was wholly overlooked by Wright, for 



