AND MYOLOGY OF THE MARSUPIALIA. 877 



Systematic. 



"When the structures described above are arranged in sys- 

 tematic order, the following results are obtained : — 



Sub-order POLYPROTODONTIA. 



Characters common to all Genera : — Lips entire. Both frenum* 

 present. Three circumvallate papillae, a well-developed sub- 

 lingua, and no lateral organs. Tonsils compact. Stomach simple 

 and has no special gland. Parotids small. Submaxillaries 

 large. Intestiiial tract short. No cervical thymus. No thyroid 

 isthmus. Post-caval vein covers aorta. Yagus and sympathetic 

 fused. 



Family Didelpiiyidje. 



Characters common to all Genera : — Oi'al vestibule smooths 

 No cheek-pouches. Duodenal loop differentiated. Caecum well- 

 developed. Thyroid gland anterior. Mammae asymmetrical. 

 Patella not ossified. 



Genus Didelphys : — Labial tubercles variable. Palatal formula 

 C9l,P-|-U — . Epiglottis conical, entire, emarginate. Lower 

 oesophagus transverely rugose. Mammae 5-13. 



Genus Metachirus : — No labial tubercles. Palatal formula 

 C^IgP — U — . Epiglottis notched. Lower oesophagus not trans- 

 versely rugose. Mammae 7-9. 



Genus Philander : — No labial tubercles. Palatal formula 

 OjjI,P-t-U — . Epiglottis has concave antei'ior border and 

 i"ounded angles. Lower oesophagus not transversely rugose- 

 Mammae 7. 



Genus Marmosa : — No labial tubei^cles. Palatal formula 

 CgloP — U — . Epiglottis with concave anterior border a.nd sharp 

 angles. Lower oesophagus not transversely rugose. Mammae 

 9-15. 



Family Dasyueid^e. 



Characters common to all Genera : — No cheek-pouches. Duo- 

 denal loop not differentiated. Caecum absent. Thyroid gland 

 anterior. No transverse oesophageal rugae. Mammae sym- 

 metrical. Patella not ossified. 



Genus Dasyurus : — Labial tubercles opposite canine teeth. 

 Oral vestibule papillose. Pala,tal formula C^jI^P-t-U — • Epi- 

 glottis thick, rounded, entire. Mammae 6-8. 



Genus Sarco2)hilus : — No labial tubercles. Oral vestibule 

 smooth. Palatal formula G.LP-[-TJ — . Epiglottis thin and 

 parts crushed together. Mammae 4. 



Family PERAMELlDiE. 



Genus Perameles : — No labial tubercles. Oral vestibule with 

 hard ridges. Cheek-pouches (?) small fossae. Palatal formula 

 O^JjP-l-U-. Epiglottis notched. No transverse oesophageal 



