MAY, 1921. AMERICAN MARSUPIAL, CENOLESTES OSGOOD. 109 



one below the posterior root of the middle premolar and a smaller below 

 the anterior root of the first molar. 



On the lingual side of the mandible the dental foramen is situated as 

 usual at the base of the angular process. In some specimens a shallow 

 groove runs along the inner side of the proximal half of the jaw but in 

 no case does its position or character seem to warrant any assumption 

 that it is a true Meckelian groove. 



The angular process is moderately inflected and subtriangular in 

 shape with a fairly wide base and a rounded but not decidedly obtuse 

 tip. The inflection is slightly less than in the majority of polyprotodonts 

 and the process is not produced into a slender prong like that in the 

 smaller dasyurids. The condyle is relatively high in position, slightly 

 more than halfway from the angle to the tip of the coronoid and extend- 

 ing well beyond a line drawn between them. In this respect, therefore, 

 it is more like Phascologale and other dasyurids than like the didelphids 

 in which the condyle is seated on a relatively short base. 



The length of the bony lower jaw is proportionately less than in most 

 polyprotodonts and this is especially true if it is considered in relation to 

 the upper jaw. In two specimens of nearly equal size, the length of the 

 bony part of the jaw in Ccenolestes is 77 per cent of the total length (in- 

 cluding terminal incisors) and that in Phascologale is 95 per cent. 



Owing to the wide variation in the lower jaws of marsupials, it is 

 difficult to draw any conclusions from the findings in regard to Cceno- 

 lestes. Miss Dederer (1909) has regarded the jaw of Ccenolestes as indic- 

 ative of polyprotodont affinity, believing it to be very similar especially 

 to Antechinomys and Sminthopsis. It differs from these in many respects, 

 as in the broader more upright coronoid, the less inflected and less 

 attenuated angle, the less divergent rami, and in the presence of a 

 foramen in the masseteric fossa, this last being a diprotodont character. 



Among the didelphids, the mandible shows considerable variation 

 and comparison is difficult. It might be said that as respects the angle, 

 C&nolestes is somewhat intermediate between Didelphis and Philander 

 and as respects other characters it shows no especial indications of 

 relationship to the didelphids more than to other marsupials. 



SUMMARY OF CRANIAL CHARACTERS. 



The great range of variation among both polyprotodonts and 

 diprotodonts leaves relatively few characters that are diagnostic of the 

 two groups. Without a complete representation of all known forms it 

 can only be said that certain characters are regarded as polyprotodont 

 or diprotodont because they are mutually exclusive in the majority of 

 forms examined. On this basis, it is clear that the skull of C&nolestes 



