117 



arches arise by a very short but coQimon stem. There is no indi- 

 cation whatever of an afferent hyoidean vessel arising either from 

 one of the first pair of afferent branchial arteries, or from the truncus 

 arteriosus between them. 



The efferent artery of the first branchial arch is prolonged ven- 

 trally and anteriorly, reaches and perforates the hypohyal, and then 

 turns upward along the anterior surface of that bone and then along 

 the corresponding surface of the ceratohyal. This is exactly as 

 described by Maurer in larvae of this fish, and the artery thus 

 described, which is said by Maurer to be developed from the primary 

 afferent artery of the mandibular arch, is the arteria hyoidea of that 

 author's earlier descriptions, but the arteria hyo-mandibularis, or 

 afferent pseudobranchial artery of his later descriptions. Just before 

 this artery, in the adult, perforates the hypohyal it sends a branch 

 upward posterior to the ceratohyal, this branch not being shown by 

 Maurer in any of his figures but having almost exactly the position 

 of the arteria hyoidea, or afferent hyoidean artery of his later 

 descriptions. But Maurer says that this latter artery, which is said to 

 be the primary afferent artery of the hyoidean arch, wholly aborts 

 in late larval stages. If this be so, the branch found in the adult is 

 quite certainly developed, as is a corresponding branch in Acipenser 

 (OsTROUMOFF, 1907), from a ventral prolongation of the posterior 

 efferent hyoidean artery, and the conditions in Amia, to be later 

 described, seeming to confirm this origin of the vessel, it is here 

 called the secondary afferent hyoidean artery. 



There are accordingly six afferent arteries found in the adult 

 Esox; four branchial arteries, a secondary hyoidean artery and a 

 mandibular artery. From the first, second and third branchial arteries, 

 near their ventral ends, a short branch is sent forward along the 

 ventral edge of the related cleft, these branches recalling the ventral 

 afferent loops found in Chlamydoselachus (Allis, 1911b). 



The secondary afferent hyoidean artery runs upward along the 

 posterior (internal) surface of the ceratohyal near its ventro-posterior 

 (external) edge, there lying along the external (anterior) surface of 

 certain of the branchiostegal rays, and along the internal (posterior) 

 surface of others. It is a small and delicate vessel and could only 

 be traced upward about one half the length of the ceratohyal. 



The afferent mandibular artery runs upward along the anterior 

 (external) surface of the ceratohyal, but it is a small and delicate 



