Henry L. Bruner 45 
is gradually reduced. Inside of the spiral fibers the muscle contains one 
or two layers of longitudinal fibers which are deeply imbedded in the 
wall of the vein. 
In Monitor niloticus (Text Fig. 6) the relations of the m. constrictor 
ven jugularis interne are the same as in Phrynosoma. In a specimen 
28 cm. long the muscle covers the vein for a distance of 3.2 mm. The 
fibers of the muscle form a close network not only around the vena jugu- 
laris interna but also about the vena cerebralis posterior, which they fol- 
low half way to the foramen magnum. The muscle fibers themselves 
are relatively slender, as are all of the striated fibers in Monitor. 
In Lacerta the relations of the m. constrictor vene jugularis interne 
are complicated by the attachment of the muscle to a free epibranchial 
cartilage,’ the second epibranchial of Parker, 84. This cartilage is an 
irregularly curved rod which extends from the roof of the tympanum to 
the floor of the pharynx. It includes (@) an oblique anterior portion, 
which arises from the lateral wall of the prominentia ampulle posterioris ; 
(b) a middle, sagittal portion, which hes on the median aspect of the 
m. constrictor ven jugularis interne ; it is provided with a strong dorsal 
ridge for the attachment of the muscle (Text Fig. 7; Fig. 3, Plate I). 
(c) The caudal portion of the cartilage bends under the jugular vein and 
around the lateral wall of the pharynx, where it lies caudal to the first 
cerato-branchial. It terminates in the floor of the pharynx a short dis- 
tance behind the caudal end of the second cerato-branchial cartilage. 
The m. constrictor vene jugularis interne of Lacerta agilis surrounds 
the vein at the terminus of the vena mandibularis and vena cerebralis 
posterior (Text Figs. 2 and 7). Ina specimen 18 cm. long the muscle 
envelopes the vein for a distance of about 2 mm., one-half of which les 
behind the mouth of the vena cerebralis posterior. The vena mandibu- 
laris enters the jugular vein anterior to the mouth of the cerebral vein 
(Text Figs. 2 and.7). The lateral attachment of the muscle hes wholly 
rostral to the mouth of the vena mandibularis; it begins about 260 
behind the anterior border of the muscle and covers 240 p. The median 
attachment of the muscle begins about 540 » behind the anterior border 
and includes about 500 », or one-fourth of the total length of the muscle. 
The constrictor muscle is composed of both free and fixed fibers. In 
the cartilaginous stage of the skull the fixed fibers arise wholly from the 
lateral portion of the parotic process (crista parotica of Gaupp, 00). 
*Cope, 98, has also observed this cartilage in Lacerta and noted its close 
approximation to the second cerato-branchial cartilage. 
