112 On Notoryctes in North-west Australia. 



more. And the nasal opening is also less in height. Palale 

 slightly more imperfect. Bulla} rather larger. 



Five anterior upper teeth small and very uniform in size, 

 i 1 scarcely exceeding the others, and the last of the five 

 (probably p 1 ) is a small simple tooth hardly equalling the 

 canine or posterior incisors. In AT. typhlops this tooth is 

 usually intermediate in size between these small anterior 

 teeth and the much larger p 3 and p 4 behind it. I 1 touches 

 its fellow of the opposite side, while the two are well separated 

 in AT. typhlops. Last molar — m 3 — small, narrow, almost 

 linear, scarcely showing any trace of the structure charac- 

 teristic of the anterior molars ; in JS r . typhlops, on the other 

 hand, the tooth is usually a reduced imitation of those in 

 front of it. 



But the chief distinction is in the lower dentition, for AT. 

 caurinus carries the reduction of the teeth in the anterior 

 premolar region one stage further than occurs in iV. typhlops. 

 As Dr. Gadow * has shown, that species varies considerably 

 in the development of the teeth of this region, so that different 

 specimens have in front of the secator (fifth tooth from the 

 back) either three full-sized teeth and a rudiment, four full- 

 sized teeth, or four and a rudiment — in the latter cases the 

 full number of ten lower teeth being present. But in 

 A 7 ", caurinus there are only three pre-secator teeth, all full- 

 sized and not rudimentary, so that there are only eight teeth 

 in the whole series. And these three teeth occupy but a 

 very short space — 2*8 mm. — in correlation with the shortened 

 muzzle of the skull, and there is no special space between the 

 last of the three and the secator next behind it. 



In some groups this difference in number would be of generic 

 or subgeneric value ; but here, where we have already in the 

 type-species a range of from what we may call 3^ to 4^ 

 teeth, commonly differing on the two sides of the jaw, the 

 further reduction to three is clearly only of specific value. 

 The lower molars are all rather smaller than in N. typhlops, 

 but there is no perceptible difference in the structure 

 of m % . With the lesser size and smaller number of the teeth 

 the total length of the lower tooth-row forms a very good 

 diagnostic character of N. caurinus. 



Dimensions of the type (measured on the dried skin) : — 



Head and body 90 mm. ; tail 12 ; nose-pad 9'2 X 5"7 ; large 

 anterior claw 13*8 X 3'3 ; second large claw 12 # 2 X 6*7. 



Skull : greatest length 23*7 ; condylo-basal length 21 ; 



* P. Z. S. 1891, p. 366. 



