110 THE DESEADO FORMATION OF PATAGONIA 
Using this species as a basis, the following are the charac- 
teristic features. The first upper incisor is a small crop- 
ping tooth, with a well-developed cingulum high up on 
the inner face, which, when the tooth is worn down to the 
proper level, unites with the main part of the crown and 
incloses for a short time a small pit. On the external face 
there is also a feeble cingulum near the base of the enamel. 
The second incisor is greatly enlarged into a caniniform 
tush. In the species L. oxyrhynca, this tooth is much 
smaller but as this reduction of the tushes is the only dif- 
ference, I consider these forms as the female. The third 
incisor is again small, and has a well-developed cingulum 
on both the front and inner faces. The canine is similar 
to inc. 3. 
The first premolar is much reduced in size, with a weak 
cingulum on the outer face, and probably another on the 
inner side (the tooth is too much worn in my specimen to 
be sure). Beginning with premolar 2, the upper teeth are 
molariform. The premolars are rectangular in outline, 
each being much wider than long, and each having a cingu- 
lum on the outer side. On the inner side, along the anterior 
half of each premolar, there is a high cingulum, which, 
though interrupted at the anterior corner, continues around 
onto the anterior face of the tooth. On a worn tooth this 
anterior cingulum unites with the grinding surface, and 
leaves a small pit in the anterior internal corner, which is 
very suggestive of Rhynchippidae. In the middle of the 
grinding surface, there is an oblique pit, the remains of the 
basin in young teeth. The molars continue to increase in 
size toward the rear. They have a vestige of a cingulum on 
the external side, no cingulum on the inner side, but on the 
anterior side for about one third the distance there is a 
cingulum similar to that on the premolars. In the middle 
of the grinding surface is an elongated oblique pit, similar 
to that in the premolars, but a little more advanced, there 
being a trace of the development of cristae. 
