158 PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 



The measurements are from a photograph of one of the Ameghino 

 specimens. 



MEASUREMENTS. 



Upper dentition, length A. to & inclusive. .057 &, length on 



1, length (i. e., antero-posterior diame- " width 0055 



ter) 004 , length 012 



i, width (t. e., transverse diameter) 006 " width 0065 



4, length 009 &-, length 014 



" width 006 " width 008 



METOPOTOXUS ANCEPS sp. nov. 



(Plates XXIV, Fig. 8 ; XXVIII, Figs. 5, 6; XXIX, Fig. 6.) 



This is a smaller and less modified species than M. Icevatus and is 

 probably a little earlier in geological date. The type specimen (Princeton 

 Mus., No. 15,612) which was collected by Mr. Peterson at Lake Pueyrre- 

 don, is a skull, without mandible, which, though somewhat damaged at 

 the anterior end and with most of the teeth broken, is yet in an excellent 

 state of preservation and quite free from distortion. 



The upper teeth (Plate XXIV, fig. 8) differ in a number of details from 

 those of the preceding species; - and - are actually and relatively 

 smaller ; - is elongate and very simple, the trilobation on the inner side 

 being very feebly marked, while in M. Icevatiis it is distinct ; - is missing 

 and of - only the posterior half remains, which shows that the median 

 external lobe is much less developed than in the other species and the 

 division of the postero-external lobe less distinct ; on - and -, however, 

 this division is quite as marked, but on - it again becomes faint. 



The skull (Plates XXVIII, figs. 5, 6; XXIX, fig. 6) is quite notably 

 different from that of any other Santa Cruz glyptodont. The occiput is 

 relatively higher and narrower than in the other species, except Cochlops 

 debilis, and has a decided forward inclination, while in all the other contem- 

 porary species (M. lavatus doubtless excepted) the plane of the occiput is 

 nearly vertical ; the occipital crest is neither very thick nor very prominent, 

 while the sagittal crest is very feebly marked and is, in fact, rather an area than 

 a crest. The basioccipital is very broad posteriorly, much wider proportion- 

 ately than in any of the preceding genera ; it rapidly narrows toward the 

 anterior end, where it suddenly increases in dorso-ventral thickness ; its 

 ventral surface is without a keel, but has a shallow median depression in 

 the posterior part. A very marked difference from all the preceding 



