56 PSEUDOCERATITES OF THE CRETACEOUS. 
involution covers up entirely the sides of the last volution, but it is obvious 
that until a late stage preceding this, it is not so complete, leaving a large 
and more open umbilicus in the young. 
Locality: North Africa. 
Age: Senonian. 
SPHENODISCID/A. 
This is a provisional group to include genera having three principal 
lateral lobes and saddles and numerous auxiliary lobes and saddles which 
are more distinctly phylliform than is usual in the Tissotidee, also having 
keeled venters. 
There are three genera: Indoceras, Libycoceras, and Sphenodiscus. The 
development of the first and second genera, and whether they have a solid 
keel, is not known, but the third has an acute venter from an early stage 
and has also a solid keel. Nearly all specimens having hollow keels 
exhibit a truncated aspect on the venter of their internal casts which is 
not shown in any figures of Indoceras and Libycoceras 
INDOCERAS Noetling. 
Indoceras has been placed in the Sphenodiscidee near to Libycoceras 
because of the external characteristics of the later stages of the type species 
described below, and because the sutures in both the species described by 
Noetling have resemblances to those of Sphenodiscus. As in many other 
published forms, there is no description of the earlier stages, and the dorsal 
sutures, which would also greatly assist in drawing correct inferences, 
are still unknown. The essential distinction between this and Sphenodiscus 
lies wholly in the fact that the saddles are entire in this genus instead of 
being divided or denticulated as in the former. 
INDOCERAS BALUCHISTANENSE Noetling. 
Indoceras baluchistanensis Noetling, 1897, Pal. Indica, Series XVI, Vol. 1, pt. 3, 
pl. 21, fig. 2; pl. 22, figs. 1-3. 
According to Noetling’s figures and descriptions, this interesting species 
at a diameter of about 40 mm. has elongated forward-bent ridges on the 
outer part of the volution that are obviously the remnants of sigmoidal 
coste. The venter at this stage is somewhat obtuse, but tending toward 
_ being subacute, with a keel bordered by smooth zones and obscure ridges 
