198 EDWARD L. RICE 
in Chelydra the sphenethmoid cartilage is entirely lacking, while 
in Dermochelys it is perfectly developed; in Chelonia it may be 
well developed or rudimentary. Emys (Kunkel, 712 b) is like 
Dermochelys in the presence of this dividing cartilage between 
the fenestra olfactoria and fissura orbitonasalis. When the 
cartilage is lacking, the ethmoid ramus of the trigeminus ordin- 
arily enters the nasal capsule in company with the olfactorius; 
in the crocodile a very aberrant course is described by Shiino 
(14). Here the ethmoid ramus passes not into the nasal cavity, 
but directly to the free upper surface of the nasal tectum, where 
it lies in the ‘sulcus terminalis,’ corresponding to the aditus 
conchae. Another unusual arrangement is described by Nick 
(712) in Dermochelys—the presence of a foramen for the external 
ethmoid ramus (for the internal ramus as well in one specimen) 
independent of the fissura orbitonasalis, which is perfectly en- 
closed in this form. The foramen epiphaniale, for the exit-of 
the external ramus, seems to be of almost universal occurrence; 
it is specifically mentioned for Sphenodon (Schauinsland, ’00), 
Vipera (Peyer, 712), Chelone and Chelydra (Nick, 712), and 
Emys (Kunkel, ’712b). In the adult of Trionyx a foramen in 
the exact position of the foramen epiphaniale is figured by Ogushi 
(11), who, however, identifies it as the ‘foramen ductus glandulae 
nasalis.’ Only in Crocodilus (Shino, ’14) is the absence of the 
foramen epiphaniale affirmed—a natural correlative of the re- 
markable course of the ethmoid nerve in this form. Data are 
scanty concerning the foramen apicale. In Crocodilus its pres- 
ence is noted by Shiino (’14); in Emys it is reported lacking by 
Kunkel (’12 b), who, however, gives no detailed account of the 
course of the ramus internus. 
8. MANDIBULAR ARCH 
1. General description 
Various parts of this structure have been more or less fully 
described in preceding pages; it is desirable now to collect these 
scattered data and to give a more consecutive account of the 
entire arch. The cartilaginous mandibular arch is composed 
