Henry L. Bruner 89 
short distance behind its fellow and supphes the posterior part of the 
muscle, which it enters below the jugular vein, close to the junction of 
the vena mandibularis with the trunk vein. 
The relations of the m. constrictor venee jugularis interna of Tropido- 
notus ate, in some respects, quite different from those of the constrictor 
muscle of the lizard. There is good reason to believe, however, that the 
VINX. 
| 
Fic. 18. Reconstruction of the m. constrictor vene jugularis interne of 
Tropidonotus natrix, from a specimen 59 cm. long. Right side. x 22. 
The bundles of muscle fibers are spiral but the details are diagrammatic. 
The individual fibers are not indicated. 
v. m., vena mandibularis; v. mxz., vena maxillaris; v. j. i., vena jugularis 
interna. 
The vena wsophagea and vena cervicalis lateralis penetrate the posterior 
half of the muscle in Tropidonotus but they are not shown in the figure. 
saurian muscle shows the more primitive relations and that the peculiar- 
ities of the muscle in Tropidonotus are due to general modifications of 
structure which occurred during the phylogeny of the Ophidia. The most 
important factor in modifying the relations of the muscle has probably 
been the development of the enormous gap and the distensible pharynx, 
