Studien zur Urgeschichte des Wirbelthierkörpers. XL 155 
falls into the internal carotid artery at the point indicateti, in fig. 5, 
having crossed towards that vessel in front of the hyomandibular 
cleft. A small branch is continued dorsad from the anastomosis 
which supplies the afferent artery of the pseudobranch; it a?iastomoses 
lüith a small branch of the carotid, escaping with the facial behind 
the hyomandibular cleft.« 
Weiterhin beschreibt Prof. Wright den Verlauf und die Ver- 
theilung der Carotiden; ich gehe darauf hier nicht weiter ein und 
will nur erwähnen, dass sie durchaus dem Verlauf bei den Selachiern 
zu entsprechen scheinen. Dann aber fährt er fort: 
y>It was chiefly from consideration of the blood-supply that 
Müller regarded the pseudobranch of Lepidosteus as the homologue 
of that of the Selachians, and it is obvious that the agreement is 
very dose ivith the condition described in Mustelus. The pseudo- 
branchs in both receive blood which has been aerated in the lower 
pari of the hyoidean demibranch, and also from a vessel, the art. 
hyoidea or hyo-opercularis of Ganoids and Teleosts, vjhich is 
derived from the ventral end of the efferent artery of the first bran- 
chial arch, also, the blood emerging from the pseudobranchs falls in 
each case into a stream directed forwards from the dorsal end of the 
efferent artery of the first branchial arch, and destined for the supply 
of the brain and the ball of the eye. In spite of this agreement, 
the explanation of which I am unable to furnish from my material, 
other morphological considerations of greater (?) weight, to be pre- 
sently adduced, appear to me to justify the conclusion that the pseudo- 
branch of Lepidosteus is the upper part of the hyoidean demibranch. 
»The condition of the parts in Lepidosteus proves that the art. 
hyoidea of the Teleosts is not the homologue of the hyoidean aortic 
arch, as is sometimes assumed , for the two vessels coexist in that 
genus. As remar ked above its course agrees with that of the thyro- 
mandibular artery of Dohm. It appear s to me to be homo-dyna- 
mous with the nutritive or branchial arter ies which spring from the 
succeeding efferent arteries , in the way this does from the first, and 
to owe its greater relative size in the Ganoids and Teleosts to the 
development of the gill-cover from the hyoid arch. The Selachians 
also possess similar nutritive vessels, and it is very easy to under stand 
why that for the hyoid arch should be larger than those for the succeed- 
ing arches , whereas it is difficult to reconcile Dohrrìs account of 
the origin of the thyro-mandibular artery with the condition in the 
stage of Mustelus described above. It is difficult to conceive an 
