612 CLASS XVII. 



has convolutions, which in the Ornithorhynchus are absent. The olfactory 

 nerves are unusually developed. 



ORDEE II. Marsupialia. 



Mammas ventral, contained in the pouch or placed between two 

 oblong, cutaneous folds. Clavicle single (furcular) perfect in 

 almost all, coracoid clavicle none. Incisor and molar teeth in all. 

 External ears in all. 



Marsupial animals. LINNAEUS united in a single genus the 

 species known to him, under the name Didelphis (didelphis from 

 8e\<f>v<s, uterus), because the pouch in which the young are received, 

 forms, as it were, a second womb, 



Compare on the propagation of these remarkable animals HOME Phil. 

 Trans. 1808, pp. 307 312, OWEN Phil. Trans. 1834, P. 2, pp. 333 364, 

 on the osteology and the classification by the same, Transact, of the Zool. 

 Soc. Vol. II. &c. See especially also his article Marsupialia in TODD'S 

 Cyclopcedia, ill. pp. 257 330. Many osteological peculiarities, especially 

 in the cranium, are observable. The occipital bone in many species (Opos- 

 sum virginianum, Dasyurus ursinus &c.) for the whole of life consists of 

 four distinct pieces; the temporal bone commonly remains divided into 

 three pieces. The great ala of the sphenoid forms an expansion (bulla) 

 similar to that formed in other mammals by the temporal bone. The bony 

 palate has, in addition to the foramina incisiva, apertures of greater or 

 less size closed by membrane. The inferior margin of the lower jaw is 

 convex and broad, as if bent inwards, especially at the angle ; this last is 

 also observed in Ornithorhynchus. Also the cavity of the cranium is very 

 small, and the cranium, however various in different genera, is on the whole 

 flatter above than in other mammals. 



For the special knowledge of the mammals belonging to this order we 

 possess, besides the first part of WATERHOUSE's./Va. Hist, of the Mammalia, 

 a smaller work by the same writer, forming the eighth vol. of J ARDINE'S 

 Naturalist 's library, Edinburgh, 1841. See also The Mammalia of Aus- 

 tralia, by J. GOULD, London, 18451852, 4 parts, folio. 



Family II. Glirina WIEGM., Rhizophaga OWEN. Incisors 



2 



^ ; a large interval between the incisors and molars, canines 



none. Feet pentadactylous, with pollex of hind feet short, un- 

 armed. 



Phascolomys GEOFFR. 1 Teeth with roots indistinct, molars with 



1 Ann. du Museum, n. (1803) pp. 364 367. The animal described by COLLINS 

 (Account of the English Colony of New South Wales, London 1802, quoted by WATER- 

 HOUSE) does not differ from this ; the number of teeth had been given incorrectly, 

 which caused ILLIGER to form the genus Amblotis (Prodromus, p. 77), a genus to be 

 discarded from the class of Mammals. 



