Pseud obrancliial and Carotid Arteries in the Guatbostome Fishes. 127 



apparently has uo orbito-nasal branch, agreeing- in this with elasmo- 

 branchs and not with teleosts. 



The external (posterior) carotid of Ceraiodus is said to be of 

 late development, and is first said (p. 203) to take "its origin from 

 the first epibranchial artery, so that it appears as the forward pro- 

 longation of the lateral dorsal aorta". Later (p. 205), it is said 

 that this artery "is derived actnally from a portion of the original 

 anterior carotid artery, and does not represent a carotid artery 

 comparable with that of any other form yet described". The artery, 

 excepting that it is shown running internal, instead of external to 

 the dorsal end of the hyoidean aortic arch, closely resembles in 

 origin and general course, the temporo-maxillaris of the Batoidei, and 

 the external carotid of Lopholatilus ; and that it contains a portion 

 of the original anterior carotid, can evidently be true only of an 

 apparently unimportant basal part of that artery. 



The mandibular aortic arch completely aborts, but is shown in 

 its embryonic position, by dotted lines, in my diagram. 



Kellicott says (1905, p. 196) that Ceratodns and the elasmo- 

 branchs are the only forms in which two efferent branchial arteries 

 develop in each arch; but he evidently oveidooked F. W. Müller's 

 figures of Lepidosteus, where two of these arteries are shown in each 

 of the four branchial arches. 



Kellicott concludes (p. 205) that the similarity between the 

 carotid arteries of elasmobranchs and Ceraiodus "is a parallelism"; 

 which certainly is not true for the internal carotid, called anterior 

 in Ceratodus and posterior in elasmobranchs. As for the external 

 carotid, if it is not an artery wholly different from that in any 

 other fish, it must be at least a serial homologue to the artery in 

 elasmobranchs, ganoids and teleosts. 



Of the arteries in Amphibia and higher vertebrates I have not 

 attempted to make diagrams, the descriptions that I have of them, 

 with a single exception only, being wholly unsatisfactory. The one 

 exception is Twining's (1906) description of these vessels in the 

 chick. According to that author, there is, in young embryos of the 

 chick, a so-called ventral carotid, which has its origin from the base 

 of the glossopharyngeal aortic arch, and is formed from basal remnants 

 of the mandibular and hyoidean aortic arches. The dorsal portions 

 of those two arches have wholly aborted in the youngest stage 

 described by Twining, a four and one-half day incubated embryo, 

 unless it be that the auricular artery represents a dorsal remnant 



