René Pourtau—The Hocene of Egypt. 65 
variety in which the periproct is unusually developed, tending to 
be nearly as broad as it is long, and penetrating the posterior 
border; E. Humet, very rare below, abounds in certain localities ; 
S. Logothett is restricted to the ‘ Alveolina Series’’, but only in 
the south; to the north it is replaced by S. varians, R. Fourtau, 
which is also limited to this horizon. Z. libyca and H. Lefebvrei 
are among the most characteristic forms and are present almost 
every where. 
In addition, the ‘‘ Alveolina Series”? yields a number of forms 
which are only prevented by their very narrow localization 
from being characteristic: such are Levocidaris miniehensis, Mayer- 
Kymar; the genus Gisopygus (two forms of which appear ata slightly 
lower horizon), which attains a splendid development in the ‘‘ Alveolina 
Series’’, to disappear almost completely with them; ephrenia 
Lorio, R. Fourtau, Schizaster miniehensis, R. Fourtau, Huspatangus 
Lamberti, R. Fourtau, and Cheopsia Mortensent, R. Fourtau. 
Thick masses of limestones containing enormous numbers of 
Nummulites gizehensis, Khr., appear above the ‘‘ Alveolina Series ”’ 
in Egypt. With them, the echinid fauna changes absolutely. The 
species we have just mentioned disappear, making way for others 
which have not yet been found in the lower strata. These are: 
Porocidaris Schmidelui, Minster, Hchinolampas africanus and its 
variety Mraasz, de Loriol, Schizaster africanus, de Loriol, S. moqatta- 
mensis, de Loriol, Huspatangus formosus, de Loriol. These forms are 
met with throughout the mass of limestones with Vummulites gizehensis, 
accompanied according to locality by less abundant species such 
as: Levocidaris Abbater, Gauthier, generally distributed, Brisso- 
_ spatangus Hume, R. Fourtau, in the southern area, Orthechinus 
mogattamensis, Cotteau, and Brissopsis Lamberti, Gauthier, in the 
northern portion. Then follow a whole series of limestones in which 
no echinids have been found. They are characterized by the 
. abundance of branching Bryozoa and Serpule. 
_ The strata above these limestones are almost lacking in Nummulites, 
but yield a special sea-urchin fauna, including: Rhabdocidaris 
Gaillardoti, Gauthier, Thagastea Luciani, de Loriol, Eehinolampas 
Cramert, de Loriol, Anisaster gibberulus, Michelin. To these may 
be added the following species, which are more rarely met with: 
Thylechinus libycus, R. Fourtau, Echinolampas moelehensis, R. Fourtau, 
in the southern area, Sismondia Blanckenhorni, Gauthier, and Clypeaster 
Fourtau, Lambert (=C. Breunigz, de Loriol, non Laube), in the 
northern portion. 
Above these deposits is a series of marly or calcareous strata 
without sea-urchins, and in the Fayum mainly containing vertebrate 
remains. 
These successive faunas enable us to establish definite divisions for 
the Eocene of Egypt. 
In the first place, we can define two main divisions of which the 
line of demarcation is easily traced in consequence of the disappear- 
ance of Conoclypeus Delanouet and the appearance of Hehinolampas 
africanus, which inaugurates the group of conoclypeiform Echinolampas, 
apparently derived from C. Delanouev. 
DECADE VI.—VOL. II.—NOo. Il. 5 
