TERTIAllY VEETEBEATA OE THE EAT0M. 
234 
l:ir<r(^ ])ost('ro-(ixtt'rn:il cusp. Tlio tnloii is oC nioiku’ute size, and its outer l)oi-(ler is high 
and I'onns a culting-edgo ; it is s(‘])aratod from the much lower inner border by a 
sliglilly concave surface, whicli is homologous with the basin-shaped depression of the 
talon in tlie other species. On the antero-external angle of the tooth there is a well- 
niarkeil tubercle (stylid) belonging to the cingulum, which is wanting round the rest 
of the crown. 
The dimensions of this specimen are : — Length, so far as ])reserved, 4d5 cm. ; depth 
of ramus beneath 3, I'tJ cm. The lengths of the teeth are: — pm. ‘k, 8 mm.; 
m. 1, G’5 mm.; ?n. 2, 8'5 mm. ; m. 3, 11 mm. 
M. 9260. Plaster cast of the above specimen. Made in the British Museum. 
Order CETACEA. 
Suborder ABClI.rEOCETI. 
Eamily ZEUGLODONTID/E. 
Facial region of skull greatly elongated ; external nares opening comparatively far 
forwards ; nasal canal prolonged backwards by the union of the maxillae, palatines, and 
l)terygoids, so that the internal nares are far back; nasal bones elongated; frontals 
forming broad supraorbital processes. Parietal region of the skull very narrow, and 
temporal fosste very large. In the earliest forms {Protocetus) the normal entherian 
dentition seems to have been present, and tlie teeth behind the second premolar 
have three roots. In the later forms [Zeitglodon) the dentition is reduced, })robably 
by loss at the hinder end of the series ; the anterior premolars may have one or 
two roots, but the other teeth of the molar-premolar series are two-rooted, and have 
compressed crowns with sharp serrated edges. The new genus Prozeuglodon described 
below^ is intermediate between these two types. 
Tlie Zeuglodonts of the Eayian are es[)ecially interesting, because the first 
mammalian bones described from this region were parts of the skeleton of a member 
of this family. In 1879 Schweinfurth collected some vertebnc, including an axis, 
from the island Geziret-el-Qorn in the lake I>irket-el-CIurun : the beds in which 
these remains were found belong to the Eirket-el-Qurun series of Peadnell, forming 
the upper part of the Lower Mokattam beds. The specimens were described by 
Dames*, by whom they were referred to three forms; — (I) a large species with 
* Silzungsb. k. preuss. Akad. AViss. vol. i. (1883) p. 129. 
