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closely accompanies the internal carotid and could be traced as far as the internal carotid foramen, 

 where it either fused with the internal carotid or vanished in the sections. The external branch 

 closely accompanies the external carotid until it reaches the facialis opening of the trigemino-facialis 

 Chamber. There it separates slightly from the carotid, but enters and traverses the trigemino-facialis 

 Chamber, lying somewhat dorsal to the carotid. Issuing from the Chamber, the vessel separates into 

 three branches. One of these branches accompanies the scierotic-iris branch of the carotid artery 

 and passes into the cranial cavity with that branch of the latter artery that traverses the little 

 foramen in the alisphenoid, already described. A second branch of the vessel closely accompanies 

 that branch of the carotid that goes to the levator arcus palatini. The third branch turns backward 

 and immediately gives ofE a small branch which accompanies that terminal portion of the carotid that 

 runs downward to fall into the arteria hyoidea. The remainder of this third branch then continues 

 backward along the side wall of the skull, joins the truncus hyoideo-mandibularis facialis and 

 traverses, with that nerve, the facialis canal through the hyomandibular. Slightly before it enters 

 the latter canal it sends a branch backward, this branch joining the ramus opercularis profundus 

 facialis and going to the region of the adductor hyomandibularis and the adductor and levator 

 operculi. The terminal portion of the third branch of the vessel x of these fishes, this branch being 

 given o£E from the external artery after that artery issues from the trigemino-facialis Chamber through 

 its trigeminus opening, thus has a distribution similar to that of a branch of the hyo-opercularis 

 of Amia given ofE before the artery enters the trigemino-facialis chamber. In Amia, in fact, this 

 latter branch is the important part of the artery, and so led me to call it the hyo-opercularis, the 

 part that enters the trigemino-facialis chamber appearing as a small branch only. 



P T E R T I C. 



The pterotic (squamosal) forms a small lateral portion of the dorsal surface, and the dorso- 

 posterior portion of the lateral surface of the brain case, and the larger part of the lateral wall of 

 the temporal fossa. The bone is bounded, as usual, by the sphenotic, proötic, exoccipital and epiotic 

 with all of which bones it is in synchondrosis, and by the lateral extrascapular, parieto-extrascapular, 

 frontal and postfrontal, with which bones it is in sutural contact. The opisthotic overlaps externally 

 the outer surface of its postero-ventral portion. On its internal surface there is a large recess which 

 leads into a canal which lodges the outer portion of the external semicircular canal, 



On the dorsal surface of the bone, near its lateral edge, there is a prominent longitudinal ridge 

 which ends posteriorly in a short sharp point which forms one of the spines of the lateral row. A 

 thin flat posterior process projects backward from the dorsal half or two-thirds of the bind edge of 

 the bone, and gives Insertion to the dorsal end of the fibrous membranes that line the anterior and 

 posterior surfaces of the opercular opening. Degenerate muscle fibers are found in the dorsal ends 

 of these membranes. No portion of the trunk muscles arises from the process. On the dorsal edge 

 of the process the lateral edges of the lateral extrascapular and suprascapular rest, but the process 

 gives no support to the supraclavicular, such as Sagemehl describes in the Characinidae and 

 Cyprinidae. On the lateral surface of the bone, close to its dorsal edge and extending nearly the 

 füll width of the body of the bone, there is an oval facet for the posterior articular head of the 

 hyomandibular, the facet lying considerably dorsal to that portion of the bone that lodges the 

 external semicircular canal. Dorsal to the anterior portion of this facet, a depression on the anterior 

 edge of the bone forms the posterior portion of the dilatator fossa. The pterotic is traversed by the 



