434 PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. 



No. No. No. No. No. No. No. No. 

 15,706. 15,707. 15,708. 15,700, 15,068. 15,624. 15,000. 0,122. 



M^, transverse diameter . . .0015 .0018 



MA, antero-posterior diameter . .0012 



" transverse diameter . . .00 1 



Posterior lower premolar, antero- 

 posterior diameter . . ..0015 .0016 .0014 .0015 .0015 .0015 .0014 

 Posterior lower premolar, trans- 

 verse diameter . . . .0008 .001 .0008 .0008 .001 .001 .0008 

 Length of inferior molar series on 



alveolar border . . . .007 .007 .008 



M T , antero-posterior diameter .0024 .0025 .0025 .0025 



" transverse " ..0015 .0015 .0015 .0015 



My, antero-posterior " . .002 .002 .002 .002 .0022 .002 



" transverse " . .0015 .0015 .0015 .0015 .0015 .0015 



My, antero-posterior " . .0017 .0016 .0018 .0018 



" transverse " . .0012 .0012 .0014 .0014 



M-f, antero-posterior " . .0012 .001 .001 



" transverse " . .0009 .0008 .0008 



Depth of mandible below posterior 



premolar .... .0028 .003 .0025 .003 .0025 

 Depth of mandible below My ..0032 .0036 .003 .0027 



" " " " Mj . .0032 .0035 



CALLOMENUS Ameghino. 



(Plate LXIV, Figs. 5, 5^.) 



Callomenus Amegh. ; Nuevos Restos Mamif. F6s. Patagonia Austral, p. 20, 

 Aug., 1891 ; Revista Argentina, I, entr. 5^, p. 306, Oct., 1891. 



Although known only from the mandible and inferior dentition, this 

 genus is probably valid, having progressed farther than Palceothentes in 

 the elimination of the vestigial antemolars, as the result of a progressive 

 shortening of the lower jaw. The posterior premolar is double-rooted, 

 but no longer reaches the general level of the molar series, as it does in 

 Palceothentes. It is overlapped and partly concealed by the sectorial blade 

 of the first molar. In view of the individual variation in the number of 

 vestigial teeth shown by some of the phalangers, Callomenus may be re- 

 garded as rather doubtfully separable from Acdestis, which retains four 

 of these teeth (Ameghino, 1903, p. 171, fig. 98) in addition to the double 

 rooted premolar. 



Callomenus :is represented in the collection by the right half of a mandible 



