Psëudobraucbial and Carotid Arteries in the Gnathostome Fishes. 123 



mandibular aortic arch has acquired a secondary connection with 

 the ventral end of the efterent giossopharj^ngeal artery, and, in this 

 26 mm larva, there arises by anterior and posterior branches each 

 of which is shown as in capillary connection Avith the corresponding 

 branch of the glossopharyngeal artery. 



In Müller's figure of this 26 mm larva the dorsal end of the 

 hyoidean aortic arch is wholly wanting. A portion of the eiferent 

 portion of the arch is said to persist as the "dorsales Randgefäss 

 des Kiemendeckels" of Müller's nomenclature, but the dorsal section 

 of the aortic arch, between this "Randgefäss" and the aorta, has 

 wholly aborted. Thinking this unusual, because of the persistence 

 of this part of the aortic arch in Amia, I looked for it in sections 

 that I have of a 55 mm Lepidosteus, and there find it as a small 

 branch that arises from the common carotid, sends a branch to the 

 spiracular cleft, and then itself takes a course in relation to what 

 I take to be, from my very superficial examination, the truncus 

 hyoideo-maudibularis facialis. Weight (1885) also quite certainly 

 found this arterj-, for on p. 484 of his work he refers to a small 

 branch of the carotid that escapes "with the facial behind the 

 hyomandibular cleft", and anastomoses with a small branch that "is 

 continued dorsal from the anastomosis which supplies the afterent 

 artery of the pseudobranch" ; the two branches together apparently 

 forming the complete dorsal end of the hyoidean arch. 



The external carotid does not, according to MtJLLEE's descriptions, 

 send a branch to the pseudobranch; and it is to be noted that this 

 carotid artery is first shown by Müllee in a 16 mm larva, a larval 

 stage in which the dorsal section of the hyoidean aortic arch is 

 first shown by him as wanting. The artery appears suddenly, well 

 developed, without any explanation. 



MÜLLEE says (1897, p. 498j that the efferent pseudobranchial 

 artei'y of Lepidosteus sends an arteria ophthalmica magna to the eye, 

 exactly as it does in Acipenser and selachians. He does not, however, 

 show this artery in any of his figures, and as Weight (1885) does 

 not mention it, and as I have failed to find it in my 55 mm larva, 

 although I have looked especially for it, MIiller must be in error. 

 There is also no choroid gland in Lepidosteus, this naturally accounting 

 for the absence of the arterj^ 



Müller shows no connection between the efferent pseudo- 

 branchial arteries of opposite sides, and he definitely states that 

 there is nowhere any such connection between the internal carotids; 



