84 



iinder-siirface white; hands and feet with (^rev-brown nietapodials and white 

 digits ; tail brown above, whitish below. Skull far smaller than in ohcsidus, 

 smooth, and almost without cranial ridges, the sagittal crest obsolete, and even 

 the two lateral thickenings of the occipital much less developed than usual. 

 Nasals much shorter and narrower than in ohcsulns. i)ullae not far from as 

 broad as in obesidus, but peculiarly shortened, rather abruptly cut off behind. 



Teeth small throughout. The three juxtaposed incisors, I'-P, together 

 about 3 mm. as compared wath 4-5 and upwards in obesidus. Canines short. 

 Secator and molars all proportionately reduced. 



Dimensions of the type (measured on the spirit-specimen before skinning) : 

 Head and body, 242 mm.; tail (damaged), 103 mm. in another rather younger 

 specimen ; hind foot, 50. 



Skull : Greatest length, 54-5 ; condylo-basal length, 53 ; zygomatic breadth, 

 25-3; nasals, 21-7 x 5-2; intertemporal breadth, 11-6; palatal length, 31; oblique 

 diameter of bulla, 103; dental length, 98; front of canine to back of M^, 205; 

 diameter of secator, 2; combined length of M^"^, 85. 



To this it may be added that this little bandicoot, which is an extremely 

 active and rather elegant little creature, is very readily distinguishable from 



Fig. 2. 



Manus of Isoodon itauticiis, showing the contrasted white of the digits, and the uhiar carpal 



vibrissae. Twice natural size. 



/. obesiilus when living examples of the two species are seen side by side. Its 

 whiter ventral surface, and its small pale manus and pes, combined with its 

 general light build, make it a very different looking animal from the sturdy, 

 more compact, and darker mainland form. In the skull, as Oldfield Thomas 

 has noted, the bullae are most distinctive, and it has been thought w-ell to 

 illustrate this point by scale drawings of the bulla region of an adult male 

 uauficHs and of a small example of obesidus. It will be noticed in comparing 

 figs. 4 and 5 that the bullae of nauticus are short and broad as contrasted with 

 those of obesulus, and that they appear to be truncated at their posterior ends. 

 One other cranial feature is worthy of note. In )iauticus the intertemporal 

 constriction is relatively considerably less than in obesulus, the skull being dis- 

 tinctly less hour-glass shaped. I have attempted to illustrate this point by a 

 method, familiar enough in anthropology but not greatly employed in the study 

 of mammals, of superimposing the outline of one skull upon the outline of the 

 other. Fig. 6 is so constructed that the middle point in the length of the two 

 skulls coincides, and from the resulting diagram it will be seen that whereas 

 the skull of nauticus is in general considerably smaller, the intertemporal con- 

 striction, at its minimum, varies but little in the two crania. Finally, the general 

 roundness of the skull and lack of muscular ridges, and the absence of sagittal 



