40 The Cephalic Veins and Sinuses of Reptiles 
dorsalis; (b) with the palatine veins, through the vena palato-cerebralis ; 
(c) an external connection with the vena cerebralis anterior; (d) an 
internal connection (secondaire Verbindung) with the vena cerebralis 
anterior. 
In Lacerta the vena cerebralis media sometimes retains its posterior 
outlet into the vena jugularis interna. 
The vena cerebralis posterior gives rise in all forms, to a vena spinalis, 
which may, perhaps, furnish an outlet for the blood of the brain. 
5. All of the forms studied show an extensive system of palatine sin- 
uses or sinus-like veins. In Lacerta and Emys these include certain 
apparently homologous parts, especially the sinus palatinus medius and 
sinus palatinus lateralis. In the snake the relations of the various parts 
are peculiar and difficult to interpret. Some of these relations are re- 
ferred to in connection with the vena maxillaris. 
6. The vena mandibularis of Lacerta, Tropidonotus, and Emys enters 
the vena jugularis interna near the posterior end of the mandible. In 
the lizard and snake the junction of the two veins occurs at a point where 
the trunk vein is surrounded by a striated constrictor muscle, m. con- 
strictor vene jugularis interne, which is described in the second part of 
this paper. This relation seems to furnish conclusive evidence that the 
vena mandibularis of the snake is homologous with the vena mandibularis 
of the lizard. 
In the turtle the vena mandibularis is a small vein which enters the 
jugular vein caudal to the constrictor muscle. It is not improbable that 
the terminal part of the mandibular vein has been utilized by the vena 
jugularis interna in order to make connection with the vena jugularis 
externa. This would also explain the lateral termination of the man- 
dibular vein in the turtle. 
In Tropidonotus the vena mandibularis is considerably enlarged, the 
right vein more than the left. Its chief tributary is the vena maxillaris. 
In the Sauria the vena mandibularis is formed by the union of two veins, 
the external and internal mandibular veins, which are connected by 
numerous anastomoses. The vena maxillaris of the lizard terminates in 
the sinus orbitalis and has no connection with the postorbital veins. 
7. The vena maxillaris shows a similar development in the lizard and 
turtle. It would probably be impossible, however, to establish complete 
homology between the saurian vein and the vena maxillaris of the snake. 
On the contrary, if we compare the anterior part of the latter vein with 
the sinus palatinus of the lizard, we find certain resemblances which do 
not seem to be accidental. The sinus-like enlargement, the relation to 
