SCOTT : LITOPTERNA OF THE SANTA CRUZ BEDS. 8 1 



Though very doubtful as to the propriety of separating this supposed 

 genus from Proterotherium, I prefer to let it stand as distinct until more 

 material shall have been obtained for deciding the question. In his 

 original description Ameghino says of it: "Les os du nez sont formes 

 par quatre pieces distinctes, les deux nasaux et deux autres os qu'on pent 

 appeler des internasaux. A peu pr^s vers le tiers en avant de leur jonction 

 avec les frontaux, les nasaux se separent formant comme les deux branches 

 d'une fourche, entre lesquelles s'intercalent les os internasaux ; ces os se 

 prolongent tr^s peu en avant des nasaux et terminent en pointe. Par la 

 position que ces os occupent on ne pent pas les regarder comme les 

 homologues des prenasaux de plusieurs mammiferes " ('94^, pp. 39-40). 

 Whether this structure represents anything more than an individual 

 abnormality, remains to be determined. 



Tetramerorhinus fortis Ameghino. 



(Plate VII, Figs. 8, 9.) 



Tetrajnerorhimts foriis Amtgh..; Enum. Synopt, etc., 1894, p. 40. 



The type and only known specimen of this species has teeth which are 

 much worn, but display no significant difference from those of Protero- 

 thermnt mistrale. The skull, as is clearly indicated in the cast, has been 

 subjected to some vertical crushing and the " internasals " have been 

 pushed down below the level of the nasals. The edges of the latter are 

 smooth and rounded and the shape of the opening made by the depression 

 is very nearly symmetrical, so that the structure is apparently not due to 

 fracture from crushing. I am inclined to believe, however, that this is 

 merely an abnormal individual of P. aiistrale, but a larger number of 

 specimens must be obtained before such a reference would be fully justi- 

 fied. The rostrum and whole nasal region are broader than is usual in 

 Proterotherium, and the supraciliary ridges are more elevated above the 

 brain-case. 



The dimensions in the following table are taken from a cast of the 

 typical and only known representative of the species. 



Measurements. 



Upper dentition, length i^-m-^ . .106 Upper premolar series, length . .045 



P, antero-posterior diameter . . .0065 Pl, length {i. e., ant.-post. diam.) . .010 



" transverse diameter . . . .0065 " width (z.^., greatest trans, diam.) .oog 



Upper premolar-molar series, length .082 P-, length ..... .0105 



