116 EDWARD PHELPS ALLIS, JR. 



in this same region, a mass of 'dense nervo-vascular' tissue 

 supplied by a branch of the mandibular branch of the carotis 

 externa, and I then thought that this tissue suggested ' ' a rem- 

 nant of glandular tissue of some sort, possibly the remnant of a 

 portion of the mandibular gill." In Polypterus, Mr. Henry 

 now also finds, in this same place, a much vasculated tissue 

 supplied by that mandibular branch of the carotis interna of that 

 fish that I (Allis, '08 b) considered as probably the persisting 

 dorsal remnant of the mandibular aortic arch. A further study 

 of the arteries in this fish now makes it plainly evident that this 

 branch of the carotis interna is simply the maxillo-mandibular 

 portion of the carotis externa, the carotis externa of my earlier 

 descriptions being simply the ophthalmic branch of that artery, 

 somewhat widely separated from the maxillo-mandibular branch. 

 I now also find that the mandibular portion of this latter artery 

 falls, ventrally, into an anterior prolongation of the lateral 

 hypobranchial artery, exactly as in selachians, and from this 

 anterior prolongation of the hypobranchial artery, before it 

 reaches the carotis externa, two delicate branches are given off 

 which quite unquestionably represent the afferent mandibular 

 artery and the anterior efferent hyal artery of the present de- 

 scriptions of Chlamydoselachus. These two delicate arteries 

 are connected by cross-commissure, as in Chlamydoselachus, and 

 then, running, one anterior and the other posterior to the nervus 

 mandibularis internus facialis, they unite as they fall into the 

 artery described by me in my earlier work as probably the hyo- 

 mandibular cross-commissural vessel. This identification of 

 this latter vessel I now find to have been correct. From the point 

 where it is joined by the two delicate arteries above described, 

 two branches arise. One of these branches runs forward, internal 

 to the muscles of the region, and joins the mandibular branch 

 of the carotis externa, thus corresponding, excepting in its re- 

 lations to the muscles, to the anterior prolongation of the hyo- 

 mandibular cross-commissure of Chlamydoselachus. The other 

 branch runs upward posterior to the spiracular canal and joins 

 the little branch said by me, in my earlier work, to supply the 

 thymus. About midway in its course it traverses a much vas- 



