526 PROFESSOR OWEN ON THE EUSTACHIAN CANALS IN CROCODILES. 
hinder opening of the long nasal passage ; and it may also be remembered, that there 
is a peculiar valve in the Crocodiles which shuts off all communication between that 
passage and the mouth. 
Description of the Plates. 
PLATE XL. 
Fig. 1. A view of the hinder part of the base of the skull of a Crocodile, showing : — 
V. The venous foramen. 
e. The median Eustachian foramen. 
el. The lateral Eustachian foramina (the canal, eV, is laid open on the right 
side). 
n. The posterior nasal aperture. 
c. The carotid foramina. 
p. The precondyloid nervous foramina. 
t. The foramen jugulare. 
1. The basioccipital. 
2. The exoccipital. 
5. The basisphenoid. 
24. The pterygoid. The bristle ending at this figure is passed through the 
median canal and right subdivision of its basioccipital branch through 
the sinus of communication with the lateral canal, which is laid open 
between t and c. 
Fig. 2. A view of an injected preparation of the Crocodilus acutus, showing the course 
of the carotids cc, vertebral artery v, and entocarotid c, to its foramen, 
and through the posterior bony canal into the tympanic cavity. 
Fig. 3. Showing the emergence of the entocarotids, c, from their anterior bony canals 
opening into the sella turcica, their sinuous course forwards, and conflu- 
ence into the single artery continued into the rhinencephalic division of the 
cranium. 
PLATE XLI. 
Fig. 4. A section of the skull of a Crocodilus hiporcatus, showing the free or promi- 
nent tubular termination of the posterior bony carotid canal in the tympanic 
cavity ; c, a style passed through the canal ; 16, the petrosal. 
Fig. 5. A section of the bony and soft parts of the palate of an Alligator {All. Indus'), 
showing the posterior nares, n, the common median valvular aperture, x, 
of the median, e, and the two lateral, el, Eustachian canals ; bristles are 
passed along the membranous portions of these tubes. 
