126 Edward Phelps Allis jr.. 



based on very careful drawings sent me hj Mr. W. F. Allen, made 

 by him two years ago, while still attached to my laboratory, from 

 dissections of injected fishes. Mr. Allen's drawings do not definitely 

 show whether the afferent pseudobranchial artery belongs to the 

 hyoidean or the mandibular arch, but as the hj'oidean gill is sup- 

 pressed in this fish it would seem as if the vessels related to it 

 would also be largely suppressed, as they are in Amia. The drawings 

 show no vessel that would seem to be the hyo-opercularis artery. 

 The internal carotid, as identified by Mr. Allen, is shown arising 

 from the pseudobranch, as its efferent artery, this arterj^ being con- 

 nected by a long and small commissural vessel with the external 

 carotid. The arrangement of these arteries is therefore as in 

 Acipenser. The internal carotids of opposite sides are connected by 

 commissure, but this commissure is intracranial in position, lying 

 between the saccus vasculosus below and the base of the brain above. 



In Cerafodus (Fig. 9), as described by Kellicott (1905), that 

 section of the dorsal aorta that lies between the dorsal ends of the 

 hyoidean and glossopharyngeal aortic arches aborts, as in the 

 Batoidei, and the hyoidean arch acquires secondary connections with 

 the efferent glossopharyngeal artery, first by means of a ventral 

 commissure, and later, by a smaller dorsal one. The internal 

 (anterior) carotid of the adult is accordingly^ formed, as in selachians, 

 by the dorsal portion of the efferent hyoidean artery together with 

 the prohyoidean portion of the lateral dorsal aorta. But, the hyoidean 

 aortic arch itself, of the adult, is said to be a secondary formation; 

 the primary arch aborting, excepting only a small dorsal remnant, 

 and a secondary arch being developed from that remnant combined 

 with what is said to be, in all probability, a branch that develops 

 upward in the hyoidean arch from the ventral end of the anterior 

 efferent glossopharyngeal artery. The internal (anterior) carotid of 

 Cerafodus thus differs from the internal (posterior) carotid of elasmo- 

 branchs only in that it may not include a strictly equivalent portion 

 of the dorsal end of the primary hyoidean aortic arch. 



The internal carotid of Ceratodus is connected with its fellow 

 of the opposite side by a commissure that lies, as is probably the 

 case in teleosts, anterior to the dorsal end of the mandibular aortic 

 arch, instead of, as in most selachians, posterior to that arch. 

 Whether this commissure in Ceratodus is extracranial or intracranial 

 can not be told from Kellicott's descriptions, but it would seem, 

 from GtJNTHEE's (1871) descriptions, to be intracranial. The artery 



