282 PATAGONIAN EXPEDITIONS! PALEONTOLOGY. 



the anterior margin of the palate and separated from - by a shorter, yet 

 considerable, diastema ; - is subcylindrical, the antero-posterior diameter 

 equalling or exceeding the transverse ; - and A are transversely oval, very 

 broad, much compressed antero-posteriorly and of nearly equal size ; - is 

 similar, but smaller. Of the mandibular dentition, T is caniniform, small, 

 subcylindrical, horizontally worn and separated from 2 by a somewhat 

 shorter diastema than that of the upper jaw; 2 and -3- are transversely 

 oval or rectangular, broad, but less antero-posteriorly compressed than 

 ^ and A , while T is again cylindrical. 



As the skull and skeleton are known only in A. giganteus, they will be 

 described in connection with that species. 



ANALCIMORPHUS INVERSUS Ameghino. 



Analcimorphus inversus Amegh. ; Rev. Argent, de Hist. Nat-, T. I, 1891, 

 p. 320. 



The type and only specimen of this species consists of a fragment of the 

 right half of the palate with the second, third and fourth teeth in place, 

 and the right ramus mandibuli, lacking the predental beak and the an- 

 gular process, but retaining all of the teeth. That the animal was very 

 young is shown by the open palatal suture, but its small size is not en- 

 tirely due to youth and it could never have approximated the large species 

 in stature. 



Except in regard to size, the dentition displays little that is specifi- 

 cally characteristic; - tends to assume a trihedral form, with the apex 

 turned forward ; ^ and - are very much compressed antero-posteriorly, 

 while ^ and - 3 - are less compressed and more rectangular and T is very 

 regularly cylindrical. 



The ventral border of the jaw is but moderately convex, and though 

 the immaturity of the animal may partially explain this, the great differ- 

 ence in the form of the mandible between this species and A. giganteus 

 cannot be entirely accounted for in this manner. The postero-external 

 opening of the dental canal is double, but, as may be inferred from the 

 analogy of Hapafaps, this is doubtless individual. 



MEASUREMENTS. 



&-, length (i. e., antero-posterior diam- -8-, length .006 



eter) 007 " width oio 



, width (i. e., transverse diameter) . . . .006 A, length 0055 



