50 PSEUDOCERATITES OF THE CRETACEOUS. 
PARATISSOTIA n. gen. Hyatt. 
Highly compressed smooth forms like the type of this genus, P. regularis 
and ficheuri, omit the characteristic nodose stages and more or less obtuse 
or flattened keeled venters of Metatissotia or else pass through them at an 
early stage, becoming later highly acute and smooth or at least without 
prominent nodes in their mature stages. In the two species examined 
they never have channeled venters at any stage. ‘The discovery of a 
hollow keel in the later stages of P. regularis would have caused me to 
separate that species from the other species referred to this group had their 
development been different and the structure of their keels also known. 
PaRATISSOTIA GROSSOUVREI (Peron). 
Tissotia grossouvre’ Peron, 1897, Mém. Soc. géol. France, Paléontologie, Vol. VII, 
No. 17, pl. 16, figs. 1, 2. 
This is similar in aspect to P. ficheuri, but is less involute, the umbilicus 
being much larger and the sutures distinct. The first lateral saddles have 
denticulated outlines instead of the smooth, phylliform arms of P. fichewri. 
The young have not been examined, but the adult appears to belong to 
this genus. 
Locality: North Africa. 
Age: Lower Senonian. 
ParatissoTia ? THOMASI (Peron). 
Tissotia thomasi Peron, 1897, Mém. Soc. géol. France, Paléontologie, Vol. VII, 
No. 17, pl. 13, fig. 3 (not pl. 16, figs. 5, 6). 
The type of this form is a compressed shell with very involute whorls 
and the zone around the umbilicus depressed and flattened. The venter, 
at least in advanced age, has a simple, not very prominent keel, 
unaccompanied by tubercles of any kind and sides almost smooth. 
The form is not sufficiently well known to be placed here without a 
query after the generic name. 
Locality: North Africa. 
Age: Base of Senonian. 
