410 MONOGRAPH OF THE AUSTRALIAN MAIiSIPOBIiANCHlI, 



and acute, the notch between them deeper than those which 

 separate them from the lateral cusps, which are much longer and 

 broader, with the inner border acute and convex, the tip pointed, 

 and the outer boi'der obtusely rounded and almost linear, not 

 separated by a groove from the basal portion of the plate; 

 mandibular plate with eleven short, blunt cusps, the outer one at 

 each side and the median one inappreciably larger; inner series of 

 discal teeth large, triangular and acute in front, broad and 

 chiselled on the sides and behind ; the middle teeth behind the 

 maxillary plate ai'e as large as the lateral ones; these teeth are 

 twenty-six in number, and the anterior pair correspond to the 

 inner maxillary cusps ; in front of the interspace between the 

 anterior pair a series of five teeth, which gradually decrease in 

 size from within, extend in a straight line to the outer rim of the 

 disk; from each of these a curved series of similarly developed 

 teeth radiates outwards and backwards on either side; the disk is 

 armed laterally with similar series of graduated teeth, each row 

 corresponding to one of the enlarged inner teeth and being so 

 strongly bent backwards towards the outer margin as to assume 

 a subconcentric appearance; the surface of the disk is divided into 

 series of low dermal ridges, on the inner posterior border of which 

 the teeth are embedded; these ridges are set so close together 

 that the teeth of one ridge overlap the succeeding ridge ; behind 

 the mandibular plate there are no teeth outside of the circum- 

 gular series; the tongue is ai'med with a single pair of dorso- 

 lateral plates, each of which is swollen and entire on its outer 

 border and bears on its inner three strong acute cusps, the 

 anterior of which is the smaller, the others being subequal; 

 the transverse ventribasal plate is strongly tricarinate on 

 its inner surface, each of the caringe being produced into a 

 long, slender cusp, the tips of which are acute and slightly 

 curved upwards ; the median cusp is as long as the outer pair. 

 The ^"ent is situated a little behind the origin of the second 

 dorsal; the length of the tail is 4 to 4| in the total length. The 

 distance between the origin of the first dorsal tin and the tip of 

 the tail is 1^ to 1| in its distance from the extremity of the snout ; 



