GREGORY — ON CiENOLESTES 
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the protoconid of the one behind it. Doctor Osgood suggests that this 
small cusp may represent a reduced metacone and that the two main 
outer cusps are derived from the styles; but, as shown in Fig. 1, the 
two main outer cusps have practically the normal occlusal relations 
of para- and metacones, while the stylar cusps of Perameles are 
here represented by the external cingulum. All this arrangement of 
shearing blades would be well adapted for cutting and dividing the 
chitinous bodies of insects. 
The fourth upper and lower molars are reduced in size precisely 
because the first three are enlarged and because there was no room for 
expansion backward without encroachment upon the space filled by the 
strong jaw muscles. 
b. Jaws. Jaw movements (as inferred from experiments with skulls 
and mandibles) remind one somewhat of those of herbivores, perhaps 
because chitinous bodies may be somewhat like grass stems in cutting 
properties. As shown in American Museum specimens of CcenolesteSy 
the lower molars move from below, upward, forward and inward. In 
using the tip of the lower central incisor the animal brings the condyle 
forward to the front part of the smooth glenoid; the dorsal edge of the 
long lower incisor shears past the compressed second and third upper 
incisors. 
Jaw muscles recall artiodactyls and especially kangaroos; but the 
most exceptional feature is the large size of the external pterygoid which 
is two-fifths the size of the internal pterygoid and double-headed, in- 
serting at base of mandibular condyle and on stylomandibular liga- 
ment. Possibly associated with forward oblique pressure of lower 
molars on upper. 
Bony jaws: upper jaw (including zygoma) on the whole rather more 
slender than in primitive insectivores; lower jaw with large areas for 
masseter and internal pterygoid muscles. 
4. Organs of deglutition and digestion. 
a. Parotid and submaxillary glands very large. 
b. Throat muscles apparently primitive and normal. 
c. Stomach with strongly differentiated glandular area forming a 
compound gastric gland, comparable in part to PhascolarctoSj Phasco- 
lomys, and Manis. Stomach unique. 
d. Large intestine relatively short. 
e. Colon short, with very small caecum. 
f. Liver relatively large. 
g. Pancreas extensive. 
