54 PSEUDOCERATITES OF THE CRETACEOUS. 
and possibly earlier, by faint coste, which bend forward onto the venter 
but do not cross the keel. These were observed on the cast alone, no 
shell being present on the parts observed. 
The young were seen only in section, and the nepionic stage was 
completely destroyed, so that the earliest part actually seen was probably 
in the ananeanie stage. The sutures were developed on the ephebic 
volution, and there is no close similarity to those of any described species 
of this genus. They have a siphonal saddle, and first lateral saddles on 
both sides more like those of Hemitissotia -djelfensis Peron than any other. 
The inner arm of this saddle is, however, bifurcated instead of being entire, 
and the outer arm is trifurcate instead of being bifurcate as in that species. 
The siphonal saddle has an inner rounded marginal like that so common 
in Sphenodiscus. There are five pairs of entire saddles on the sides, inside 
of the first pair. The lobes more than the saddles are like those of Peron’s 
species, but they are more symmetrical in outline and longer and narrower 
in proportion. It is interesting, however, to note that its nearest affine in form 
is also an African species, Paratissotia grossouvrei of Peron. This is close 
enough in external aspect to have been considered identical but for the 
sutures, which are quite different. Peron’s form also appears to have had 
a solid keel. The surfaces of the septa and the dorsal sutures differ from _ 
those of Paratissotia serrata in that there are only four broad zygous saddles 
and lobes on the dorsum, and the saddles are directly connected with the 
external saddles by broad ridges that flex the floor of the septa correspond- 
ingly. The internal wings of the septa are also straight. The antisiphonal 
lobe, so far as seen, seems to be much broader than in that species. 
The young must have been similar to that of Paratissotia serrata in 
form, and keelless until the neanic stage was reached. ‘The keel was at 
first solid and then became hollow. 
Locality: Cachiyacu, Peru. 
Age: Upper Cretaceous, probably Senonian. 
Incertae sedis. 
TissoTia cossoni Peron. 
Tissotia cossont Peron, 1890, Moll. Crét. de la Tunisie, pl. 16, figs. 1, 2. 
This is a large fossil, 248 mm. in diameter, with acute venter exactly 
similar to Sphenodiscus in aspect and evidently extremely aged, as shown by 
