1895.] SOTJTH-AMEB.ICAK MARSTTPIAL. 8*73 



The vacuity, judgino; from the spicules of bone which project into 

 it from the nasals, and from its known development in the 

 Ruminants, probably tends to ossify over as life advances, but — ■ 

 the specimen being old — evidently never entirely fills up. 

 Interorbital space broad, smooth and rounded, with scarcely a 

 trace of ridges, ledges, or postorbital processes ; lambdoid ridges, 

 however, fairly well developed. Lacrymal canal single, just on 

 the rounded edge of the orbit. Zygomata slender, boldly expanded ; 

 malar as usual running back to form part of the glenoid fossa. 

 Palate very imperfect, the anterior foramina reaching from between 

 the third pair of incisors to halfway between the anterior and 

 middle premolars ; posterior vacuities extending from the large 

 posterior premolar to behind the last molar, the bridge between 

 their front limit and the back of the anterior foramina only 

 2'7 mm. across. Pterygoid processes slender and delicate, pointing 

 backwards and inwards, their needle-like ends 1"6 mm. long. 

 Bullae small, imperfect, transparent, formed as usual by the 

 alisphenoids. Tympanic annular, but imperfect, only forming 

 about three-foui'ths of a circle. 



Dentition. I. | ; C. j ; P. | ; M. |x2=46. 



Viewed as a whole, the teeth present a considerable resemblance 

 to those of the Australian Dromicia (e. g. D. hpida, figured Cat. 

 Mars. B. M. pi. xn. figs. 2-5), especially in their relative 

 proportions. 



Uj)per Jaw. — Incisors four in number ; the first vertical, pointed, 

 touching its fellow of the opposite side, but separated from i^, in 

 fact very similar to its condition in Didelphys. ^ and if flattened 

 laterally, not pointed, but with a straight cutting-edge ; i^ separated 

 from i', smaller and rather more pointed ^ Canines well-developed, 

 as in average carnivorous Marsupials. Anterior and middle pre- 

 molars small, narrow, two-rooted, sharply pointed, equal in size, 

 the distance between them about equal to that behind the canine. 

 Posterior premolar somewhat similar, but twice as large and rather 

 thicker transversely, with one long main cusp, which stands up 

 just higher than any cusp on the molars, and a small anterior 

 secondary cusp, placed slightly internally. Molars low-crowned, 

 with low rounded or scarcely pointed cusps, not unlike those of 

 Petaurus or Dromicia ; the two anterior square, quadricuspidate, 

 although apparently ^ there are only three roots to each tooth, the 

 postero-internal cusp being placed on a sort of flange overhanging 

 the palate and not supported by a root ; third molar similar, but 

 without the extra postero-internal cusp ; last molar minute, tri- 

 angular, as small in cross-section as the last incisor. 



Lower Jaw. — Anterior incisor elongated, exactly as in typical 



1 On the left side (as shown in Plate L.) this tooth has been displaced and 

 pressed against the front of the canine, but on the right side, which appears to 

 be normal, there is a small diastema. 



^ It is at present impossible to be quite certain as to the number of roots 

 each tooth possesses, as the teeth are so firmly wedged in that without damaging 

 the skull, as yet unique, they cannot be pulled out or their roots developed. 



