Henry L. Bruner 21 
mandibular artery and nerve. In the anterior part of its course the 
vein forms occasional anastomoses with the vena mandibularis externa 
which lies laterad from the mandible. Near the angle of the mouth the 
vena mandibularis interna divides into two parts: a pars dorsalis (v. m. 
i. d., Text Figs. 2 and 3), which runs caudad through the dorsal part of 
the mandible, and a pars ventralis (v. m. 1. v., Text Figs. 2 and 3), 
which follows Meckel’s cartilage and the ramus mandibularis V. In 
front of the articulation of the jaw the pars dorsalis enters a large fora- 
men, f. articulare, which penetrates the mandible in a transverse direc- 
tion and furnishes a passage way for the vena communicans anterior, the 
ramus recurrens cutaneous mandibularis V. and a small artery. Here 
the pars dorsalis meets the vena communicans anterior, an anastomotic 
vein from the vena mandibularis externa, then expands to form the 
sinus articularis (s. a., Text Figs. 2 and 3), a small sinus which lies in 
a concavity on the medial side of the mandible just below the articulation. 
From the caudal part of the sinus articularis the pars dorsalis of the 
vena mandibularis interna again enters the mandible and joins the pars 
ventralis, which approaches the articulation accompanied by the chorda 
tympani. The reconstructed vein runs caudad, accompanied by the 
chorda tympani, until it reaches a point posterior to the articulation, 
where the vein and nerve issue through the same foramen upon the 
dorsal surface of the mandible. Here the vena mandibularis interna 
forms a junction with two anastomotic veins: a peripheral one and a 
central one. The larger central vein is the vena tympanica anterior 
(v. t. a., Text Figs. 2 and 3), which runs dorsad close to the anterior 
wall of the tympanic cavity and on the median side of the chorda 
tympani. ‘The vein enters the vena jugularis interna near the roof of the 
tympanic cavity. The peripheral vein, vena communicans posterior, is a 
short transverse vessel which is connected laterally with the vena mandi- 
bularis externa. 
At its junction with the vena tympanica anterior and vena communi- 
cans posterior the vena mandibularis interna of Lacerta ends. This con- 
dition is probably not a primitive one, however, for in other lizards, as 
previously stated, the vein joins the vena mandibularis externa behind 
the tympanum. The change which has occurred in Lacerta will be more 
apparent after a brief description of the vena mandibularis interna of 
Cnemidophorus and Agama. 
In mature embryos of Cnemidophorus sexlineatus I find, in front of 
the articulation of the jaw, a sinus articularis, which is connected anas- 
tomotically with the vena mandibularis externa and also with the sinus 
