56 The Cephalic Veins and Sinuses of Reptiles 
partly on a posterior process of the subiculum infundibuli of Gaupp, oo. 
In addition to the forms previously mentioned the m. protrusor oculi 
has been observed in the following: 
Chameleon vulgaris Cuvier. 
Agama colonorum Daudin. 
Moloch horridus Gray. 
Anolis caroliniensis Cuvier. 
Sceloporus undulatus Latreille. 
Platydactylus mauritanicus Linnaeus. 
Cnemidophorus sexlineatus Linnaeus. 
The m. protrusor oculi is innervated by twigs from the ramus ad. m. 
depressorem palpebre inferioris of Fischer, 52, which springs from the 
motor portion of the ramus mandibularis V, passes downward and forward 
and enters the posterior ventral angle of the protrusor muscle (r. d. p. 1., 
Figs. 4 and 5, Plate 1). Within the muscle the nerve gives rise to two 
or three neryi protrusores ocul, while the nerve trunk continues for- 
ward through the ventral part of the muscle to reach the m. depressor 
palpebree inferioris. 
The embryonic development of the m: protrusor oculi is contempora- 
neous with that’ of the other musclés of the orbital region. In a Scelo- 
porus embryo with head 2100 » long the first fibers are in process of 
formation and the muscle is functionally mature when the embryo is 
hatched. In the stages examined there is no evidence of a foreign 
derivation. The innervation, however, shows a close phylogenetic rela- 
tion to the m. depressor palpebre inferioris. 
The functions of the m. protrusor oculi are sufficiently clear from its 
relations to the vena jugularis interna and the sinus orbitalis. By the 
contraction of its posterior portion the ventral fascia is elevated and 
the vena jugularis interna is compressed against the eye muscles, which 
form a sort of cushion between the vein and the subiculum infundibul 
(S. t., Fig. 5, Plate I). The anterior part of the muscle elevates, and 
gives tension to, the fascia which underlies the sinus orbitalis. 
e. THe Muscutus Protrusor OcuLi ACCESSORIUS. 
The m. protrusor oculi accessorius is a hitherto undescribed muscle 
which has been found in only a few forms. In Monitor niloticus (m. p. 
c. a., Fig. 2, Plate III; Fig. 1, Plate II) the muscle is a broad sheet of 
striated fibers which fits loosely upon the posterior part of the bulbus, 
from which it is separated by the sinus orbitals. The muscle arises chiefly 
