MARSUPIALIA. 795 



The third premolar is most prominent ; its posterior edge is generally worn 

 so as to be acute. There are no external cingula on the premolars. The 

 elevation of the external cingula of the true molars is such as to produce, 

 on wearing with the middle cusps, two triangular areas, of which the an- 

 terior is a little smaller than the posterior. The inner lobe of these teeth is 

 more nearly opposite the anterior than the posterior triangle, giving a 

 straight anterior and oblique posterior outline to the crown. There is no 

 posterior basal cingulum on the true molars. The inner lobe of the fourth 

 true molar is compressed and acute, and sends a sharp edge to the base of 

 the small cusp which represents the posterior external triangle of this tooth. 



The fourth inferior incisor is not larger than the others, and is directed 

 a little more upwards than they. The inferior canine is large, but smaller 

 than the superior, though similar in form. There is no interspace between 

 the canine and first inferior premolar; but a short one between the first and 

 second premolars, and a shorter one between the second and third premolars. 

 The crowns of these teeth are a simple cusp, which is mainly over the 

 anterior root. In all the true molars the anterior triangle is not much more 

 elevated than the posterior, and the anterior and posterior cusps of the inner 

 side of the former are well separated from the external cusp, which much 

 exceeds them in size. The anterior triangle of the first true molar is a little 

 narrowed. The cusp of the internal side of the posterior triangle is about 

 as high as the anterior cusp. In many specimens there is a small cusp be- 

 hind this one ; in some specimens it is very small, while in others it is 

 wanting. This peculiarity I at one time thought characteristic of another 

 species, the P. tricuspis. This I do not now believe to be the case, but find 

 that that species possesses other and more reliable characters. The heel of 

 the last inferior molar of the P. fugax is somewhat narrowed, and always 

 presents thi-ee cusps. 



There ai-e two mental foramina — one, the larger, below the first pre- 

 molar; the other below the fourth molar, counting from either end of the 



series. 



Measurements. 



M. 



Leugth of superior molar series plus the superior canine 013 



Length of premolar series 0052 



Length of molar series 0063 



