214 THE DESEADO FORMATION OF PATAGONIA 
is present and carries a rounded shelf. The paracone is 
the chief cusp, and is developed as a high central pointed 
denticle. The metacone is not developed as a cusp, but is 
represented by a long slanting ridge to the rear, the apex 
of which has been fused to the paracone. ‘The last upper 
molar is better developed than in most Santa Cruz genera, 
consisting of a high median cusp, the paracone; a small 
anterior cusp, the anterior external style; and a shelf-like 
posterior cusp, the protocone. Lower premolars I-3 are 
simple two-rooted teeth, each carrying a single cusp on 
the crown. ‘The fourth premolar carries a well marked 
paraconid in front, a large median protoconid on the rear 
of which is a tiny metaconulid; and a tiny talonid or heel 
which is without a basin and consists of a single tiny cusp. 
The molars are all of the same character as the last pre- 
molar. ‘The lower jaws are united by a ligamentous sym- 
physis. 
Ameghino distinguished four species, P. lacerans, P. 
tenax, P. mitis, and P. tenuis, in the order of their size. 
The last two are but little known but are quite certainly 
another genus. . 
Pharsophorus lacerans Ameghino 
P. lacerans Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 503. 
The species was founded on a lower jaw with the roots 
of the incisors, canine, and first two premolars, and with 
the remaining teeth intact. We did not find the species, 
: 
Tas 
Fig. 139. Left mandible—1/2 natural size, after Ameghino. 
