DWARF CROCODILES AND DIMINUTIVE MAMMALS, 153 
Admitting, for Mr. Hulke’s argument, that the outer nostrils of 
a Crocodile, with their dense tegumentary boundary, could, like 
those of a seal, be shut by the action of a sphincter, exclusion by 
such narial opening of the watery element would not affect its 
entry by the mouth forced open by the seized and struggling 
mammal. 
The question is, supposing the water to be stopped out of the 
anterior aperture, how is it to be excluded from the posterior one 
of the narial canal and at the same time from the entry of the wind- 
pipe? 
And here comes the point for consideration in. the comparison of 
Mesozoic and Neozoic Crocodiles with relation to their enemies and 
their prey. 
In all the Crocodiles contemporary with ‘‘ large mammals ” there 
is a double valvular structure at the back of the mouth which pre- 
vents the water that may fill and be flowing through the mouth 
from getting into either the hinder nostril or into the glottis. One 
valve is fleshy and membranous; it hangs from the hind part of 
the palate, and answers to our “ velum palati:” the other valve is 
peculiarly Crocodilian, at least in size and shape; it is a broad 
gristly plate which rises from the root of the tongue, carrying with 
it a covering of the lingual integument ; and, when the palatal valve 
is applied to it, they form together a complete partition-wall, closing 
the back of the mouth, between which and the back nostril it is 
situated ; it may be compared to a broad epiglottis, shutting off the 
glottis from the mouth. 
To make this complex mechanical structure available, the back 
nostril is singularly reduced in size, and such reduction is shown in 
the skull. ‘The small relative palato-narial orifice in proccelian or 
Neozoic Crocodilia is truly striking when contrasted with the size 
of the palato-nares in lizards and in amphiccelian or Mesozoic 
Crocodilia *. 
But this is not the only character or condition of the proccelian 
palato-naris which renders the adaptation of the valyular machinery 
available for its purpose. In Neozoic Crocodiles the palato-naris is 
placed far back—further back than the basihyal—and its plane, 
instead of being horizontal, is tilted up at the angle, which makes 
the operation of the two parts, or ‘“ folding-docrs ” of the partition, 
most effective in closing the oral chamber posteriorly y. 
What the modifications of the soft soluble parts of the hyoid and 
* This, indeed, deceived De Blainyille and Bronn as to the homology of the 
palato-nares in Teleosawrus; see ‘ Abhandlungen iiber die Gavialartigen Rep- 
tilien der Lias-Formation,’ fol. 1841, pp. 12, 16, 24. 
+ See my “ Anatomy of the Sharp-nosed Crocodile (Croc. acutus, Cuv.),” in 
the Proceedings of the Committee of Science &c. of the Zoological Society of 
London, October 25, 1831, part i. p. 189—in which, after comparison with 
the Hgyptian Crocodile (Croc. suchus, Geof.), I ‘explained the uses of the 
apparent closure of the fauces, in which, on looking into the mouth, no orifice 
or passage for the food was perceptible ; and remarked on the necessity for so 
