EDENTATA OF THE SANTA CRUZ BEDS. 26 1 



HAPALOPS PRIMUS (Ameghino). 



Mecorhimis primus Amegh. ; Enum. Synopt. des Mamm. Foss. de Pata- 



gonie; 1894, p. 157. 

 Mechorhinus primus Amegh. ; Sec. Censo de la Repub. Argent. ; T. I, 



1898, p. 200. 



It may seem quite incredible that so many as twenty-two species of a 

 single genus should have coexisted in the same region, but there are many 

 independent reasons for believing that they did not all exist at the same 

 time. A more minute study of the Santa Cruz beds than has yet been 

 practicable will very probably demonstrate their divisibility into several 

 zones, each characterized by its own species. Further, it should be re- 

 membered that the twenty-two species of Hapalops admitted in the pre- 

 ceding pages are of a very provisional character, and that more extensive 

 and better preserved material may necessitate the union of many of 

 these so-called species. Even with that now at command, it is obvi- 

 ous that there are several groups of species, the members of each group 

 or series being more nearly connected with one another than with those 

 of other groups. One such series, characterized by broad cranium and 

 rostrum, elongate premaxillaries and predentary beak of the mandible, is 

 composed of H. rectangularis, indifferens, longiceps, robustus, aguirrei and 

 brachycephalus ; a second series, with long and narrow skull, short pre- 

 maxillae and mandibular beak, is made up of H. elongatus, rostrattis, 

 atlanticus, ruetimeyeri, gracilidens, and angustipalatus and other similar 

 series might be readily constructed. It is not at all impossible that it 

 may become necessary to unite these twelve supposed species into two, 

 and yet this is not likely, both on account of the stratigraphic reasons, 

 and because of the great differences of size which such a fusion would 

 involve. Decide these questions as we may, the variability of the 

 species of this genus is most surprising. 



HYPERLEPTUS Ameghino. 



(Plate LIV, figs, i, i) 



Hyperleptus Amegh.; Rev. Argent, de Hist. Nat., T. I, 1891, p. 155. 

 f Eucholczops Amegh., in part; Ibid., p. 323. 



Hyperleptus Amegh. ; Enum. Synopt. des Mamm. Foss. de Patagonie ; 

 1894, p. 151. 



