360 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. 



Metacarpal V, length .......... .0245 



" " width at proximal end ....... .0102 



" " " " distal " . . . oil 



BORHY/ENA EXCAVATA Ameghino. 



(Plates XLIII; XLIV ; XLV, Fig. i ; XLVI, Fig. 4; LII, Figs. 2, 6; LIII, Figs. 4-4/7. ) 



Borhycena excavata Amegh.; Enum. Syn. des Especes de Mammiferes 

 Fossiles des Formations Eocenes de Patagonie, p. 121, 1894; Bol. 

 Acad. Cordoba, p. 377, 1894. 



A remarkably perfect skull (No. 15, 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 . .062 



