Sinclair: typotheria of the santa cruz beds. 
5i 
the floor of which is perforated by numerous foramina situated in both the 
parietal and the squamosal. The latter is dilated, as in Protypotherium , 
and firmly coossified with the mastoid and the auditory meatus. 
The back of the skull (PI. VIII, fig. 19) is circular in outline superiorly, 
with strong rugosities on the occipital surface for muscular attachment. 
The distended squamosal and mastoid are broadly exposed, but the suture 
between them can no longer be distinguished. The occipital elements 
are likewise completely fused, as in Protypotherium. As in that genus, 
the occipital is constricted transversely, the mastoid foramen perforating 
the suture between the mastoid and the occipital at the point of greatest 
constriction of the latter. The foramen magnum is circular in outline 
and the condyles obliquely directed and semicylindrical in shape. 
The palate is deeply concave anteriorly, but posteriorly the concavity is 
about the same in degree as in Protypotherium. The sweep of the tooth 
rows is lyrate, approaching horizontality back of the first molar. The 
anterior palatine foramina are large, extending posteriorly beyond the 
premaxillo-maxillary suture. The posterior palatine foramina emerge 
opposite the fourth premolar on the maxillo-palatine suture, or a short 
distance anterior to it. The palatines extend well back of the last molar 
and terminate in a pair of very large, heavy, triangular processes propor- 
tionately much larger than in Protypotherium and similarly supported ex- 
ternally. The pterygoid appears to have been small and scale-like, though 
it is not preserved in any of the specimens available, nor can the shape of 
the posterior narial border be determined. The bullae are pear-shaped 
and considerably flattened anteriorly, where most prolonged, as in Proty- 
potherium. The auditory meatus is long, tubular and directed almost 
horizontally. The basi-occipital is keeled inferiorly, as in Protypotherium. 
The arrangement of the cranial foramina is the same as in the latter genus. 
The mandible is short, heavy and very deep (PI. VIII, figs. 16, 25), 
with the rami firmly coossified, without trace of suture. The symphysis 
is pronate, tapering anteriorly, as in Protypotherium. Back of the symphy- 
sis, the depth of the mandible rapidly increases until a maximum is 
reached at a point vertically below the third molar. Beyond this point, 
the angle rapidly decreases in depth. As in Ptoty pother ium, it extends 
well beyond the condyle and has the inferior and posterior border inverted, 
inclosing a large submaxillary fossa. The coropoid process is sharp- 
pointed and slender, with strong posterior inclination. The coronoid 
