EDENTATA OF THE SANTA CRUZ BEDS. 217 



No. 9,176. No. 15,596. 



Rostrum, width at anterior end .033 



Palate, length in median line 049 .048 



" width at 1 02 1 .028 



" " " preorbital fossae 026 .028 



" "3. 015 .015 



" "i 014 .014 



HAPALOPS ELONGATUS Ameghino. 



(Plates XXXVII, Figs. 1-3, 5; XXXVIII, Figs. 1-3, 5; XXXIX, Figs. 1-3, 5; 



XL, Figs. 3, 4'; XLI.) 



Hapalops elongatus Amegh.; Rev. Argent, de Hist. Nat, T. I, 1891, 



p. 316. 



Hapalops brevipalatus Amegh.; Ibid., p. 316. 

 Hapalops siibquadratus Amegh.; Ibid., p. 317. 

 Xyophorus sulcatus Amegh.; Ibid., p. 320. 

 Schismotherium patagonicum Mercerat ; Rev. del Mus. de la Plata, T. II, 



1891, p. 9. 



Stenocephahis hybridus Mercerat; Ibid., p. 12. 

 Eurysodon nasutus Mercerat; Ibid., p. 19. 



To this most variable and protean species are here referred all those 

 members of the present genus which agree in the following respects: (i) 

 The caniniform teeth are small and of laterally compressed, oval section ; 

 (2) the molariform teeth are transversely rectangular, except T , which is 

 subcylindrical ; (3) the skull is relatively elongate, narrow and slender, 

 with narrow muzzle and usually well-defined preorbital fossae; (4) the 

 occipital crest is thinner and better defined than in most of the other spe- 

 cies of the genus and the supraoccipital is but moderately reflected upon 

 the roof of the cranium ; (5) incompletely adult animals a low sagittal crest 

 is present upon the frontals, but not upon the parietals ; (6) the mandible 

 has a relatively short, pointed predentary beak and the postero-external 

 opening of the dental canal is upon the ascending ramus. 



It is quite possible that more extensive and better preserved material 

 may show that certain of the names in the list of synonyms given above 

 represent distinct species, but, at present, no such separation is practicable, 

 for most of these supposed species have been founded upon very incom- 

 plete and unsatisfactory types and in accordance with characters which are 

 extremely inconstant. 



