612 EDWARD PHELPS ALLIS, JR. 
sel apparatus of the spiracular gill while the branchial rays of 
the hyal and branchial arches always lie posterior to the artery 
of the related arch. This statement, which is doubtless true 
for conditions found in embryos, with which I am not familiar, 
is not true for those found in the adult. In the adult Mustelus 
I find the afferent branchial arteries lying anterior to the bran- 
chial rays, but the two efferent arteries of each branchial arch 
lie, one anterior and the other posterior to those rays. In the 
hyal arch the single efferent artery lies posterior to the rays, and 
this would naturally be the position of the single artery in the 
mandibular arch if that part of this artery which is related 
to the spiracular gill is developed as are the corresponding 
arteries in the posterior arches. The spiracular cartilage, 
derived from the dorsal ray of the mandibular series, 
would then be in proper relation to the efferent artery of that 
arch, while the symplectic cartilage of the Teleostei, derived 
from one or more of the middle rays of the series, and lying ven- 
tral to the persisting gill, would be in proper relation to the af- 
ferent artery. 
Gegenbaur says (’72, p. 202) that both Henle and Miller 
called the spiracular cartilage of the Torpedinidae the cartilago 
pterygoidea, and compared it with what was later described by 
Huxley in the Teleostei as the metapterygoid. Parker (’76) also 
calls the cartilage in Raia the metapterygoid, and says (I. ¢., p. 
219) that it ‘‘answers td the otic process of an Amphibian;”’ 
and Huxley (’76) says the same of the spiracular cartilage of 
Cestracion. My conclusions, if correct, thus confirm these earlier 
determinations in so far as the homology of the spiracular carti- 
lage of.the Batoidei with the otic process of the Amphibia is con- 
cerned, but as this otic process is represented, in teleosts, in a 
part of the lateral wall of the trigemino-facialis chamber, it is 
not the homologue of the metapterygoid of those fishes, nor is 
it the homologue of a part of the palatoquadrate of selachians, 
as Huxley concluded. ; 
The several cartilages that have been described as spiracular 
cartilages in different selachians are certainly not all of them 
homologues of the spiracular cartilage of the Batoidei. This is 
