Henry L. Bruner 23 
extends caudad to the posterior limit of the teeth. The outlet of the 
sinus has not been definitely located, but its position suggests a close 
relation to the mandibular veins. The sinus dentalis can be readily 
seen through the mucous membrane in the living Lacerta; it has also 
been observed in sections of Agama colonorum, in which it is well filled 
by a natural injection of blood. 
(2) Vena Bucco-mandibularis (v. b. m., Text Figs. 2 and 3).—This 
anastomotic vein arises from the yena buccalis lateral to the base of 
the tongue. It runs caudad and laterad, first between the mylohyoideus 
muscle and the oral mucous membrane, then under the mandible; it joins 
the vena mandibularis externa near the angle of the mouth. 
(3) Vena Communicans Anterior (c. a., Text Figs. 2 and 3).—This 
vein arises from the vena mandibularis externa behind the junction of 
the latter with the vena bucco-mandibularis. From its origin it runs 
through the foramen articulare and joins the sinus articularis on the 
median side of the mandible. 
In embryos of Lacerta and Cnemidophorus the sinus articularis is also 
connected with the sinus prooticus, and thus continuous communication 
is established between the yena mandibularis externa and the vena cere- 
brals media. 
(4) Vena Quadrata (v. q., Text Fig. 2).—This is a small vein which 
emerges from the anterior surface of the quadrate bone directly above 
the articulation of the jaw. Passing through a notch in the quadrate 
bone the vein reaches the lateral aspect of the articulation and joins the 
vena mandibularis externa. The vena quadrata has two small tribu- 
taries: one from the median side of the mandible, the other from the 
posterior part of the m. temporalis and the adjoining skin. 
(5) Vena Commumniecans Posterior (c. p., Text Figs. 2 and 3).—Lat- 
eral to the posterior part of the articulation the vena mandibularis ex- 
terna forms a small ring which gives rise to the vena communicans pos- 
terior. This vein runs mesad and joins the vena mandibularis interna 
behind the articulation, as already described. Through the vena com- 
municans posterior and vena tympanica anterior the vena mandibularis 
externa is placed in communication with the vena jugularis interna. 
f. VENA CEREBRALIS POSTERIOR. 
(v. c. p., Text Fig. 2; Figs. 2 and 3, Plate I.) 
The two vene cerebrales porteriores are sinus-like veins which are 
formed by the bifurcation of the vena longitudinalis cerebri at the dorsal 
margin of the foramen magnum. Both veins leave the skull through the 
