38 ‘he Cephalic Veins and Sinuses of Reptiles 
palatinus medius, which begins at the rostrum and extends caudad, in 
the middle line, to a point just behind the choane. In front of the 
choane the sinus receives, on each side, a vein from the median wall of 
the nasal cavity. Behind the choane the sinus palatinus medius divides 
into two branches, which diverge from the middle line and discharge 
into (b) the sinus palatinus lateralis. This sinus begins behind the 
dentary portion of the intermaxillary bones, where the two sinus palatini 
laterales and the sinus palatinus medius meet in a common anastomosis. 
Each sinus palatinus lateralis extends caudad under the posterior part of 
the sinus orbitalis, into which it discharges through a short vessel which 
lies median to the suture connecting the palatine parts of the maxillary 
and jugal bones. 
Near its posterior end the sinus palatinus lateralis receives the vena 
mazxillaris. This is for the most part an intraosseous vein which is en- 
closed in the same bony canal with the arteria mavxillaris and the ramus 
maxillaris V. Approaching the posterior end of the maxillary bone the 
vein and nerve bend mesad, emerge from the bone and enter the large 
foramen suborbitalis, through which the vein bends ventrad to join the 
sinus palatinus lateralis. 
b. VENA CEREBRALIS MEDIA. 
This vein leaves the cranial cavity through the trigeminal foramen, 
on the outside of which it runs downward and forward to join the vena 
jugularis interna. The extracranial portion of the vein corresponds ap- 
parently to the vena cerebralis media secunda of Grosser and Brezina. 
In Emys this vein is connected with the sinus orbitalis by a vein of con- 
siderable size, which lies in the angle between the cranial wall and the 
pterygoid process of the parietal bone. ‘The vein lies on the lateral aspect 
of the ramus ophthalmicus V, and both vein and nerve are extracranial. 
This vein includes presumably, the secondary connection of the vena 
cerebralis media and the ventral end-piece of the vena cerebralis anterior. 
ce. VENA CEREBRALIS POSTERIOR. 
This vein, which is the chief efferent vessel of the brain in Emys, 
arises from the posterior end of the vena longitudinalis cerebri and 
leaves the cranium in two parts, one of which passes through the foramen 
magnum, the other through the foramen jugulare. Outside of the skull 
the two branches of the vein unite, the trunk vein running laterad to join 
the vena jugularis interna under the parotic process. The ring formed 
