Vil STOMACH OF KANGAROOS I 
ios) 
_ 
genus to genus. The stomach is much sacculated. The dental 
formula is 1? C19 P2M4. The atlas is often open below, 
forming thus an incomplete ring. . 
Though the number of the incisor teeth im the adult 
Diprotodonts is never more than three on each side in each jaw, 
nore numerous rudiments are present. Mr. M. Woodward * has 
lately investigated the subject with interesting results. He 
finds that many species present decided traces of two additional 
incisors, raising the total to that which characterises the Poly- 
protodontia ; but in two cases, viz. Macropus giganteus and Petro- 
gale penicillata, a sixth is present, the total number being thus 
in excess of that found in any other Marsupial. This, as the 
author himself admits, proves too much. No mammal is known 
which in the adult condition has so many incisors; nor do the 
fossil Mammalia help us to get over the difficulty ; even among 
reptiles it is not usual for so many teeth to occur upon the 
premaxillaries. 
It is a curious fact that the two long lower incisors can be 
used after the fashion of a pair of scissors, or rather a pair of 
shears. Their inner edges are sharpened, and they are capable 
of some motion towards and away from each other; by their 
means erass is cropped. 
The stomach of Macropus (and of other allied genera) is 
peculiar by reason of its long and sacculated character; the 
oesophagus enters it very near the cardiac end, which is bifid. 
Messrs. Schiifer and Williams” have shown that the squamous, 
non-glandular epithelium of the oesophagus extends over the 
greater part of the stomach, only the pyloric extremity and one 
of the two cardiac caeca being lined with columnar epithelium. 
The Macropodidae are clearly divisible into three sub-families, 
which are distinguished by marked anatomical characters. 
In the sub-family MacropopinaE (including the genera 
Macropus, Petrogale, Lagorchestes, Dorcopsis, Dendrolagus, Onycho- 
gale, and Lagostrophus) there is no hallux, and the tail is hairy. 
The oesophagus enters the stomach near the cardiac end. The 
caecum when short has no longitudinal bands; the liver has a 
Spigelian lobe. 
The second sub-family, PoTOROINAE or HyPpsIPRYMNINAE (in- 
cluding the genera Potorous, Aepyprymnus, Bettongia, and Calo- 
1 Proc. Zool. Soc. 1893, p. 450. 2 Tbid. 1876, p. 165. 
