120 EDWARD PHELPS ALLIS jr., 



to the anterior parts of the brain, while the other accompanies the 

 nervus olfactorius. 



At the point where the artery breaks up into its three principal 

 parts it apparently sent a branch across the base of the brain to join 

 its fellow of the opposite side, but this could not be satisfactorily 

 established. 



The hyo-opercularis artery of my earlier descriptions (1, p. 497) 

 is, at this age, a small and unimportant branch that usually arises 

 from the common carotid close to the point where that artery has 

 its origin from the etierent artery of the first branchial arch. In the 

 specimen cut in horizontal sections it arose from the latter artery 

 close to the point of origin of the common carotid. This so-called 

 hyo-opercularis artery must not be confounded with the hyo-oper- 

 cularis artery of certain descriptions of Teleosts, this latter artery being 

 the one usually called the arteria hyoidea, that is, the hyo-mandibularis 

 of Maurer's later descriptions, and the hyoideo-opercularis of Joh. 

 Müller. How I happened to select the name hyo-opercularis for 

 this artery in Amia^ I am unable now to say, but it is evidently, 

 though wholly by accident, a better application of the term than the 

 one usually made, as will appear later. The artery, in 12 mm larvae, 

 runs upward and slightly forward, and then outward, to the ventral 

 surface of the truncus hyoideo-mandibularis facialis, but could not be 

 satisfactorily traced beyond that point. As it undoubtedly has the 

 same course and distribution as in 50 mm larvae, to be later described, 

 it is so shown in the diagrams. 



This finishes the description of the arteries in 12 mm larvae, as 

 far as I have traced them, and the difierences found in older and in 

 younger specimens can now be indicated. 



In 14 mm larvae, and in all older specimens, the adult included, 

 that were examined, the alïerent pseudobranchial artery of Wright's 

 descriptions is found, this artery thus being of secondary formation. 

 It arises from the dorsal surface of the pseudobranch, and running 

 forward and mesially unites with the external carotid immediately 

 after that artery issues from the trigeminal foramen. In these older 

 specimens the primary afferent artery becomes relatively less and less 

 important, and possibly disappears entirely in the adult, as it is said 

 to do in Esox (5, p. 250), though this was not investigated. 



In 50 mm specimens (Fig. 6) the primary allèrent pseudobranchial 

 artery is still found, being, at this age, a small artery which connects, 

 around the ventral surface of the pseudobranch, near its hind end, 



