44 PSEUDOCERATITES OF THE CRETACEOUS. 
Locality: Northern Africa. 
Age: Lower Senonian. 
SUBTISSOTIA PERONI n. sp. Hyatt. 
Buchiceras ewaldi Peron, 1890, Moll. Crét. de la Tunisie, pl. 15, figs. 1, 2 (no other). 
Tissotia ewaldi Peron, 1897, Mém. Soc. géol. France, Paléontologie, Vol. VII, No. 
17, p. 68. 
This is based on a specimen from Tunis, of a diameter of 107 mm. It 
is figured by Peron as having an entire keel throughout, although the 
rounded tubercles on either side of the ventro-lateral angles have almost 
disappeared at a stage when in his ewaldi var, africana they would have 
become elongated and very coarse and the keel have been resolved into 
elongated tubercles. The venter is also entirely distinct in this species, in 
its sharper outline and more prominent keel. These features are also 
associated with peculiar sutures. The sutures of Tissotia africana have a 
long, well-defined ventral lobe, the sides of the first laterals being abrupt, 
whereas in this fossil there is a very short, ill-defined ventral lobe, with the 
sides of first lateral saddles denticulated and sloping. The first lateral 
saddles are deeply divided in 7. africana, while in this the division is not so 
well marked. The resemblances in form and sutures between this and 
T. levigata show that they are closely related. 
Locality: North Africa. 
Age: Base of Senonian. 
SUBTISSOTIA AFRICANA (Peron). 
Tissotia ewaldi var. africana Peron, 1897, Mém. Soc. géol. France, Paléontologie, 
Vol. VII, No. 17, pl. 11, figs. 1-6. 
Ata diameter of 54 mm. the young figured by Peron is a very gibbous 
form, in which the broadest diameter of the last volution measures about 
39 mm. The keel is continuous and prominent even on this cast, and there 
is a line of prominent tubercles on either side along the ventro-lateral 
angles. In the aged specimen, figured at diameter of 108 mm., these have 
become elongated, and the sides being less gibbous the venter is flatter, and 
on this volution the keel begins to disappear, becoming resolved into 
elongated nodes. There are no costz figured on these casts. Peron con- 
siders this identical with Tissotia robini, as figured by Grossouvre, but robina 
