vii STOMACH OF KANGAROOS 131 



genus to genus. The stomach is much sacculated. The dental 

 formula is I f C J^p P f M f . The atlas is often open below, 

 forming thus an incomplete ring. 



Though the number of the incisor teeth in the adult 

 Diprotodonts is never more than three on each side in each jaw, 

 more numerous rudiments are present. Mr. M. Woodward l 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 grass 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. Schafer and Williams 2 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 MACROPODINAE (including the genera 

 Macropus, Petrogale, Lagorchestes, Dorcopsis, Dendrolagvs, Onyclio- 

 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 HYPSIPHYMNINAE (in- 

 cluding the genera Potorous, Aepyprymnus, Bettongia, and Calo- 

 1 Proe. Zool. Soc. 1893, p. 450. 2 Ibid. 1876, p. 165. 



