TEETIAEY VEETEBEATA OE THE FAYt^M. 
Ii04 
iivailablo arc in bad ]n-oservation and further material is necessary before any detailed 
comparison with teeth of other genera is possible. 
SluH, of Eotherium. — I'lie skull and mandible of a ])rimitive Sirenian from the 
limestones of the Mokattam Hills has recently been acquired by the Geological 
Museum in Cairo and is important for comparison with Eosiren. The horizon from 
which these specimens come is lower than that from which the Fayum remains were 
obtained, and is probably the same as that in which was found the cast of the cranial 
cavity which Owen made the type of Eoth erhim (ogyptiacum. This skull and mandible 
Tnay in fact be referred to Owen’s species, though in some respects it differs from the 
brief description of some new material of that Sirenian lately published by O. Abel 
AVh en this author has |)ul)lished his complete account of the Egyptian Eocene Sirenia 
it will no doubt be possible definitely to determine these specimens ; meanwhile the 
fact that they represent a more generalized form than Eosiren, and are from a lower 
horizon in the same region, is sufficient to justify the comparison of the two types. 
The skull in question (text-fig. 66) is nearly complete, but the anterior portion has 
been compressed in such a way that the rostrum has been straightened, instead of 
bending down as, judging from the mandible, it must have done in the living animal; 
the anterior ends of the premaxillm have been separated by a fracture, the result 
of which is that this region has the appearance of having been more elongated than 
was actually the case. 
The occipital condyles are very large and are more sessile than in Eosiren ; in the 
mid-ventral line they are separated by a sharply defined notch. Eaterally the 
exoccipitaJs [exo.) are produced downwards into strong paroccipital processes {'pp-) 
which extend below the level of the condyles ; there is a large condylar foramen 
opening at the bottom of the groove between the base of the paroccipital process and 
the occipital condyle. The sutures between the exoccipitals and hnsioccipital [hoc.) 
are not ch ar, but that between the basioccipital and the hasispliciioid (hsp.) is marked 
by a transverse ridge, which crosses the basis cranii just behind the level of the ]iosterior 
edge of the veitical plates of tlie pferp/oids (pt.), which are closely united above with 
the basisphenoid. Above the foramen magnum (f ni.) the occipital surface is broad, 
much broader than in Eosiren, and somewhat like the same region \\\ Mceritherium [sog 
El. VIIE fig. 1 b). The snpraovci})ital [soc.) is gently concave from side to side; its 
upper border is greatly thickened and forms a great part of the massive lambdoidal ridge. 
In the middle line in front it thrusts a blunt triangular process between the posterior 
ends of the parietals ; laterally its upper angles form prominent backwardly directed 
bosses of bone, to the anterior face of which the parietals are closely united. The upper 
* “ Die Sireiien der niecliterraiK'n Tertiiirl>ilJuitgi'ii Oesicrreic-hs,’’ Abli. k.-k. gcol. Eeiclisaiist. vol. xix. pt. 2 
(Vieniui, 1904). 
