C EVANE TE oxay, 
RODENTIA——TILLODONTIA 
Order IX. RODENTIA’ 
SMALL to moderately large animals, furry, sometimes with spines. 
Toes with nails of a claw-hke character, or sometimes approach- 
ing hoofs. Usually plantigrade, and only occasionally and 
partly carnivorous. Canine teeth absent; incisors long and 
strong, growing from persistent pulps, and with enamel only or 
chiefly on the anterior face, producing a chisel-shaped edge ; 
molars few (two to six), separated from the incisors by a wide 
diastema. Caecum (nearly always present) very large, and often 
complicated in structure. Brain, if not smooth, with few furrows, 
the hemispheres not overlapping the cerebellum. Surface of skull 
rather flat; orbits not separated from temporal fossae; malar 
bone in middle of zygomatic arch; palate very narrow, with 
elongated incisive foramina; articular surface for lower jaw 
antero-posteriorly elongated. Clavicles generally present. Testes 
generally abdominal. Placenta deciduate, and discoidal in form. 
The Rodents are a very large assemblage of usually small, 
sometimes quite minute, creatures, embracing an enormous 
number of living generic types. They are distributed all over 
the world, including the Australian region, and, being small and 
often nocturnal, and by no means particular in their diet, have 
managed to thrive and multiply to a greater extent than any 
other group of living mammals. They are chiefly terrestrial 
creatures, and often burrow or live in ready-made burrows. 
1 See especially Tullberg, ‘‘ Ueber das System der Nagethiere,”’ Act. 4h. Upsala, 
1899 ; and Alston, Proc. Zool. Soc. 1875yp. 61; and for nomenclature, Thomas, Proc. 
Zool. Soc. 1896, p. 1012 ; and Palmer, Proc. Biol. Soc. Washington, xi. 1897, p. 241. 
