328 PATAGONIAN EXPEDITIONS : PAL/EONTOLOGY. 



Ameghino has referred two additional species to this genus, but the 

 material is too fragmentary for satisfactory determination. The references 



are as follows. 



PLANOPS OBESUS Ameghino. 



Eucholceops infernalis Amegh., in part; Contrib. al Conoc. de los Mam. 



Fos. de la Repiib. Argent, 1889, PI. XXXIX, fig. 8. 

 Planops obesus Amegh.; Rev. Argent, de Hist. Nat, T. I, 1891, p. 322. 



PLANOPS CYLINDRICUS Ameghino. 

 Hapahps cilindricus Amegh.; Rev. Argent, de Hist. Nat, T. I, 1891, 



p. 318. 

 Planops cylindricus Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- 



gonie, 1894, p. 164. 



PREPOTHERIUM Ameghino. 



(Plates LIX, Figs. 2, 2" ; LX, LXI.) 



Prepotherimn Amegh. ; Rev. Argent de Hist. Nat, T. I, 1891, p. 158. 

 Eucholczops Lydekker, in part; Anales del Museo de La Plata, T. Ill, 

 1894, p. 95. 



It is a curious fact that, save for the teeth, little or no direct comparison 

 can yet be made between this genus and Planops, because the parts that 

 are known in the one are not yet known in the other. Much doubt there- 

 fore remains as to the propriety of separating the two and, even admitting 

 the validity of the distinction, we cannot yet be quite certain that all the 

 species referred to Prepotherimn actually belong together. 



So far as may be judged from the extant material, the teeth are very 

 constant in their character for the genus as a whole and for each of its 

 constituent species and there is no such puzzling variability as occurs in 

 the other two families of Santa Cruz Gravigrada. The two series of upper 

 teeth, which in Planops are parallel, have a distinct convergence back- 

 ward ; A is small, subcylindrical, horizontally abraded and followed by 

 a considerable diastema ; the molariform teeth are well spaced apart, of 

 elliptical form, very broad transversely and much compressed antero- 

 posteriorly ; a is the largest of the series, while - and & diminish regularly 

 in size. In the lower jaw, T is like the corresponding upper tooth, ^ and 

 -5 are transversely elliptical, while 4 tends to a subcylindrical form. 



