15 
with anterior and posterior branches, which first supplies the trapezius 
muscle and then, extending forward into the hyoidean arch, there 
supplies the hyoideus muscle of VETTER's descriptions. 
In the hyoidean arch there is, as I interprete the vessels, no 
epibranchial prolongation of the efferent artery, the latter artery 
ending dorsally at the dorsal end of the hyoidean hemibranch and 
there being connected by dorsal commissure with the anterior efferent 
artery of the first branchial arch. Any other interpretation of the 
vessels would require the assumption of the complete fusion of the 
epibranchial portions of the hyoidean and first branchial arteries, or 
the complete abortion of the latter artery; either of which assump- 
tions seems improbable. ALLEN shows neither an epibranchial pro- 
longation of the hyoidean artery nor a dorsal commissure connecting 
it with the first efferent branchial artery. 
From the efferent hyoidean artery, somewhat dorsal to the middle 
of its length, the internal carotid artery of Arzkn’s figure has its 
origin, the basal portion of this artery being formed by the homologue 
of the definitive afferent pseudobranchial artery of the Selachii and 
Batoidei, its middle portion by the homologue of the efferent pseudo- 
branchial artery of those fishes, and its distal portion by the terminal 
portion of the internal carotid; the definitive afferent and efferent 
pseudobranchial arteries of Chimaera forming, because of the absence 
of a pseudobranch, a single continuous vessel. Running forward, this 
artery, which is the anterior carotid of Parker’s (1886) descriptions 
of Callorhynchus, passes outward over the hind edge of the carti- 
lage hy’ of Huprecut’s (1876/7) descriptions of Chimaera monstrosa 
and reaches the external surface of that cartilage. There it sends 
a branch downward along the antero-lateral aspect of the ceratohyal, 
this branch extending nearly the full length of the ceratohyal 
and approaching but apparently not connecting with the ventral end 
of the efferent hyoidean artery. This branch of the anterior carotid 
is quite certainly a persisting portion of the afferent mandibular 
artery, and in Callorhynchus, where PARKER calls it the mandibular 
artery and considers it to represent the mandibular aortic arch, it is 
connected ventrally, by longitudinal commissure, with the efferent 
hyoidean artery, as in selachians; the efferent hyoidean artery being 
also connected by ventral longitudinal commissure with the efferent 
first branchial artery. 
After giving off this mandibular branch, the anterior carotid 
