SPHENODISCID 2. ont 
on either side In later stages the venter becomes planoconvex, the keel 
and lateral ridges having disappeared. These characteristics are very 
similar to those of Sphenodiscus plewrisepta. The sutures have entire phylli- 
form saddles that resemble those of Sphenodiscus more than those of 
Tissotidee. The first lateral saddles are described by Noetling as being 
bifid in this species, and as becoming split up into separate saddles during 
development. There appear to be three principal lateral saddles in the 
fullgrown. 
Locality: Mazar Drik. 
Age: Upper Senonian. 
INDOCERAS ACUTODORSATUM (Noetling). 
Sphenodiscus acutodorsatus Noetling, 1897, Pal. Indica, Series XVI, Vol. I, pt. 3. 
pl. 21, fig. 3. 
This shell has the usual acute volutions of Sphenodiscus, but the 
sutures have the entire saddles of Indoceras. In fact the only distinction 
appears to be that the first pair of saddles are not yet completely separated, 
but appear to be branches of a first lateral. It might be said, therefore, 
that this species had only two principal lateral saddles, the first and second, 
the first being deeply bifid. If we reckon the sutures as having three entire 
principal lateral saddles, two of which are not yet fully separated, the 
species passes into Indoceras. 
LIBYCOCERAS Hyatt. 
This genus is founded upon a single species, which has, however, such 
a peculiar combination of characters that it can not be incorporated with 
other genera. Zittel recognizes the affinity of this form to Sphenodiscus 
and describes it as having three principal lateral saddles. The sutures 
have phylliform entire saddles and simply digitated lobes, and resemble 
those of the young of S. lenticularis after they have passed through the 
stage in which both saddles and lobes are entire. The median lateral line 
of tubercles and broad costz connecting these with an outer line of nodes 
along the edge of the venter and distinct keel are, however, quite different 
from the tubercles and costze and solid acute venter of Sphenodiscus, which 
has distinct sutures, and also different from Jndoceras, which has similar 
sutures. 
“AifuKos, Libyan. 
