86 
continuous: upper posterior molars (M 2, 3) each with a shal- 
low valley extending inwards from the anterior portion of the 
inner wall, and with two or three deep depressions in the 
inner half: lower molars (PM 3, M 3) with two (anterior 
and posterior) more or less defined crescent-shaped ridges: 
canines small. 
MACRAUCHENTIIDAE, 
** Skull with the basioccipital comparatively narrow forwards: 
with the nasal bones produced forwards and terminating in 
a free narrowed surface; the supra-maxillary bones with an 
upward developed expansion (connected with the nasal 
bones) and widely separated above in front. Dental series 
interrupted by wide diastemas: upper molars (PM 2, M 1, 2, 
3) each with a deep valley extending obliquely inwards from 
the median portion of the inner wall and a shallow one ex- 
tending from the angle or posterior wall: lower molars (PM 
2, M 2) with two (anterior and posterior) crescent-shaped 
ridges: canines well developed. 
XLIX.) 
PALAEOTHERIIDAE. (L.) 
b. Upper (as well as lower) true molars without a continuous outer 
wall, but (M 2-3, at least,) each with two complete transverse 
crests. (Lophiodontoidea.) 
1. True molars as well as pre-molars in part (PM 2, 3, 4) nearly 
similar, squarish, and each with the anterior crest marginal, but 
with an anterior cingulum terminating in a cusp at the antero- 
outer angle of the tooth; hindmost molar (M 3) with no posterior 
lobe. Anterior feet with four toes; posterior with three, (in 
known types). 
TAPIRIDAE, (LI.) 
2. True molars and pre-molars differentiated from each other; the 
former oblong, with the anterior crest remote from the anterior 
margin and continuous with a small crest recurrent from the 
outer wall: hindmost molar with a posterior lobe; (pre-molars 
not bilophodont but with a lobe extending inwards from the 
inner wall). Anterior feet with four (?) toes; posterior with 
three (?). 
LOPHIODONTIDAE, 
B. Nasal region compressed and extended forwards, the supramaxil- 
lary bones excluded from the nasal aperture; the nasal bones 
elongated and extending far forwards, and articulated with the in- 
termaxillary bones. Molars (M 1], 2, 3) of upper jaw each with two 
transverse rows of tubercles (3|3) separated by a transverse valley 
and with a cingulum anteriorly and internally: (lower molars dis- 
similar). (Pliolophoidea.) 
PLIOLOPHIDAE. 
(LIT) 
(LITI.) 
a 
\ . om 
