Henry L. Bruner 101 
Blut-sinus, welches einen grossen Theil des Orbitalbodens einnimmt.” 
There can be no doubt, therefore, in regard to the presence of some 
mechanism for obstructing the outlet of the sinus. 
d. TESTUDINATA. 
1. TRIONYCHIA.—Trionichide.. Aspidonectes spinifer LeSeur. ‘The 
m. constrictor ven jugularis interne is present in a late embryo. 
2. orypropirA.—K inosternide. Kinosternon pennsylvanicum Gmelin. 
A mature embryo was examined; m. constrictor vene jugularis interne 
is present. 
Emydide. Cistudo (Emys Wagl.) europea Schneider and Terrapene 
carolina have been examined. The m. constrictor ven jugularis interne 
is strong in both species. 
The foregoing list includes representatives of seven suborders of the 
Sauria, four suborders of Ophidia, and two suborders of Testudinata. 
The occurrence of the separate muscles of the swell mechanism is as 
follows: 
The m. constrictor vene jugularis interne is present in all species 
examined (Sauria, Ophidia, and Testudinata), excepting Chameleon 
vulgaris, Platydactylus mauritanicus, and Rhineure floridana. 
The m. protrusor oculi is present only in the Sauria, in which it occurs 
in all forms examined, excepting Rhineura floridana. 
The m. protrusor oculi accessorius is also limited to the Sauria, in 
which it has been found only in the Nyctysaura (Platydactylus) and 
the Thecaglossa (Monitor). 
In the foregoing review we have found the swell mechanism present 
in all species examined, excepting a few aberrant forms. If this result 
is a fair index of the distribution of the mechanism, it probably occurs 
in all typical species and familes of the Sauria, Ophidia, and Tes- 
tudinata. 
B. PHYLOGENY OF THE SWELL MECHANISM. 
It is evident from the preceding observations that the swell mechanism 
is not confined to a few isolated reptihan forms, which might, perhaps, 
have produced analogous mechanisms along entirely independent lines. 
In spite of the somewhat divergent characteristics of the mechanism in 
the different orders and families of reptiles, we find certain parts, notably 
the m. constrictor venee jugularis interne, which are almost universally 
present. The homology of such parts is suggested both by their mor- 
