SINCLAIR: MARSUPIALIA OF THE SANTA CRUZ BEDS. 387 



the Canon de las Vacas (No. 9134, American Museum of Natural History), 

 and North Gallegos (No. 15,703). 



Cladosictis lustratus may be readily recognized by the long, narrow, 

 depressed skull, with tapering muzzle, moderately expanded arches and 

 low inclination forward of the facial profile. The summit line of the long 

 sagittal crest is practically horizontal. The anterior superior premolar is 

 separated by a short diastema from the canine and by a larger interval 

 from the median premolar. The median and posterior premolars are 

 almost in contact at the alveolar border. The lower premolars are sep- 

 arated from the canine and from each other by diastemata, which vary in 

 width considerably in different individuals. The posterior premolar and 

 first molar are separated in some specimens by a short interval. 



With the exception of smaller size and less robust build, the skeleton, 

 so far as it has been possible to make comparisons, is exactly the same 

 as in Cladosictis petersoni, and the description already given in character- 

 izing the genus will apply equally to both. 



Within fairly well defined limits, there is considerable individual varia- 

 tion in size. This is probably sexual, as the difference between extremes 

 is not greater than between the sexes in Thylacynus (cf. Thomas, 1888, 

 p. 261). The range of this variation is well brought out in the accom- 

 panying measurements of the two individuals selected for illustration 

 (Nos. 15, 170 ; 15,046), which are regarded respectively as male and female. 



MEASUREMENTS. 



No. 15,04.6. No. 15,170. 



Skull, extreme length, premaxillae to lambdoidal crest .142 .158 

 " widlh across jugal arches .... .066 approximately .076 



" interorbital width 022 .0258 



Face, length, premaxillae to anterior border of orbit . .052 -O57S 



Cranium, length to anterior border of orbit . . . .090 .1005 



" width at postorbital constriction . . . .010 .0115 



Nasals, length 052 



" width anteriorly ...... .008 



" " posteriorly 024 .023 



Palate, length . .069 .079 



" width between posterior premolars (approximate) .0125 .015 



" M-i 030 .0323 



Mandible, length .1105 -H95 



" height of coronoid above angle . . . -039* .051 



" transverse diameter of condyle . . . .0152 .0162 



* Slightly decreased by fracture of the angle. 



