ORDINAL TYPES OF MOLARS: MARSUPIALIA 



of the tritubercular crown. The secondary development of a number of 

 sharp piercing cuspules seems here as in the Insectivora (p. 117) to 



Notoryctes, the Marsupial Mole 



pas mt* rr?t* 



be correlated with insectivorous diet. 

 (Figs. 61, 62) has tritubercular upper 

 and lower molars ; in the upper molars 

 the high pointed protocone is at the 

 apex of a V, formed by two ridges 

 diverging downward and outward to 

 the basal external portion of the 

 crown, ending in the para- and meta- 

 cone respectively ; on the internal or 

 lingual side, at the base of the crown, 

 the V is surrounded by a deep U- 

 like internal cingulum The lower 

 molars reverse this pattern except 

 that they lack the U-like cingulum.* 

 According to Gidley the principal 

 cusp (marked pi') is really the para- 

 cone + metacone, the protocone ap- 

 pears as an internal ledge (marked 

 cing), but there is no evidence for 

 this except analogy with the supposed 

 case in Insectivora (see pp. 124, 22V). 

 The molars of the Bandicoot (Pcra- 

 mcles, Figs. 59, 60) show a general 



parallelism with those of Didclpli'us, G-aleopithecus, certain Moles and 

 Shrews, and certain Eocene Artiodactyls (Ccenotherium, Tapirulus) in 



Fiu. 59. Molars of Perameles macri'j-n fivm 

 a specimen in the Yale Museum, xf. ^4, Crown 

 view left upper molars. B, Crown view left lower 

 molars. C, Upper and lower molars in opposition, 

 as seen obliquely from the outer side and below. 



711 



FIG. 60. Diagram showing spatial relations of the patterns of the upper and lower molars 

 when in cont&ct of Perameles maerura, (Cf. Fig. &.>). Compare the somewhat similar pattern of 

 the molars in the Mole, and in 



several respects. First the mesostyle is doubled (ws 1 , ///*") permitting 

 the formation of two complete triangles from the paracone, metacone, 

 and styles of the upper molars. Second, the lower molar pattern consists 



* [As in other mammals without a talonid in the lower molars, the protocone is much 

 elevated. The internal ledge (tiny.) appears to correspond with that in CJvrysochloris 

 (Fig. 68). ED.] 



H 



