Henry L. Bruner 35 
nasal opening. Here the vein bends mesad, under the palatine process of 
the intermaxillary bone, and discharges into the vena mavillaris lateral 
to the anterior anastomosis of the two maxillary veins. 
The vena rostralis has two important tributaries, the vene nasales 
externe, dorsalis and ventralis, which run forward, one above, the other 
below the external nasal opening. ‘The dorsal vein (v. n. e. d., Text Fig. 
4) discharges into the dorso-lateral part of the vena rostralis. It has 
its origin in the fold which forms the median dorsal boundary of the 
nasal opening. It drains a system of small blood-spaces which surround 
the anterior part of the duct of the external nasal gland. In a medial 
direction these blood-spaces occupy the meshes of a small smooth muscle, 
m. subnasalis of the author, 97. Laterally the blood-spaces extend be- 
hind the nasal aperture and join a similar system of blood-spaces which 
hes in the ventral lip of the opening. These ventral blood-spaces dis- 
charge for the most part into the vena nasalis externa ventralis (v. n. 
e. v., Text Fig. 4), a subcutaneous vein which begins a short distance 
behind the nasal opening and runs forward, under the opening, to dis- 
charge into the lateral part of the vena rostralis. 
The blood-spaces (s. v. n., Text Fig. 4) drained by the venz nasales 
extern represent the sinus vestibuli nasi of the hzard, but this sinus is 
much reduced in the snake on account of the shortening of the nasal 
vestibule. The trabecule between the blood-spaces contain smooth 
muscle fibers and the structure is otherwise very similar to that described 
in the lizard. 
In the sea snake, Hydrophis, the sinus vestibuli nasi is greatly en- 
larged (s. v. n., Fig. 4, Plate II), as are all of the veins and sinuses of 
the anterior part of the head. 
(2) Sinus Subnasalis (Text Fig. 4).—This sinus lies in the roof of 
the mouth in front of the choane. It discharges into the venze maxil- 
lares at their second anastomosis, rostral to the openings of Jacobson’s 
organ. The sinus subnasalis includes (1) a sinus subnasalis transversus 
(s. s. t.), a short transverse vessel which lies in the submucosa directly in 
front of the choanez; (2) a sinus subnasalis medius (s. s. m.), which runs 
in the median line from the sinus subnasalis transversus to the anterior 
anastomosis of the two vene maxillares; (3) a paired sinus subnasalis 
lateralis (s. s. l.), which runs parallel with the last, from the sinus sub- 
nasalis transyersus to the vena maxillaris. Between the median and 
lateral sinuses, on each side of the head, lies an opening of Jacobson’s 
organ. In the submucosa behind this opening arises (4) a short sinus 
subnasalis intermedius (s. s. 1.), which extends caudad and opens into 
the sinus subnasalis transversus. 
