PATAGONIAN EXPEDITIONS I PALEONTOLOGY. 
360 
Metacarpal V, length .......... .0245 
“ “ width at proximal end ....... .0102 
“ “ “ “ distal “ on 
Borhycena excavata Ameghino. 
(Plates XLIII ; XLIV ; XLV, Fig. 1 ; XLVI, Fig. 4; LII, Figs. 2, 6; LIII, Figs. 4-4A) 
Borhycena excavata Amegh.; Enum. Syn. des Especes de Mammiferes 
Fossiles des Formations Eocenes de Patagonie, p. 12 1, 1894; Bol. 
Acad. Cordoba, p. 377, 1894. 
A remarkably perfect skull (No. 1 5, 120), five cervical vertebrae, an incom- 
plete posterior dorsal, a fragment of the left scapula and two sternal seg- 
ments are referable to Borhycena excavata. This material was collected 
by Mr. Peterson from the Lower Santa Cruz beds ten miles south of Coy 
Inlet. 
B. excavata may be readily identified by the strong contraction of the 
facial portion of the skull just anterior to the infraorbital foramen. As a 
result of this contraction, the shape of the tooth row is rendered strongly 
crescentic, with the canine and anterior premolar offset externally to a 
greater degree than in B. tuberata. The palate retains the same width 
from the canine to the median premolar, while in B. tuberata its width 
steadily increases posteriorly. The skull is smaller than in the latter 
species, the arches more abruptly expanded and the sagittal and lamb- 
doidal crests lower. The interorbital tract is not as flat as in B. tuberata , 
the postzygomatic portion of the brain case is relatively less elongate and 
the infraorbital foramina are larger. 
The associated skeletal parts are smaller than in B. tuberata , but do 
not differ in structure sufficiently to require separate description. 
Measurements. 
Skull, length on median basal line 187 
occipital condyle to tips of premaxillae ..... .195 
“ width across zygomatic arches ....... .140 
“ interorbital width 056 
Face, length 0655 
Cranium, length to anterior border of orbit , . . . . . .133 
width at narrowest part of brain case 0245 
Occiput, height 051 
“ width 
