TISSOTIID®. 45 
is a costated compressed species with a continuous keel, even in extreme 
age, after the disappearance of the lines of tubercles, according to Grossouvre’s 
figure. His ewaldi is similarly figured as a compressed shell, but not in 
extreme of age apparently. This species is evidently distinct from T.ewaldi 
figured by Peron in his Mollusques Crétacés de la Tunisie, which attains a 
large size, and at an advanced age still has an entire keel and rounded 
tubercles. The resemblance of the youngof this species to the more mature 
stages of Subtissotia inflata and intermedia is apparent, if Grossouvre is 
correct in his assignment of the smaller casts figured to this species. 
Locality: North Africa. 
Age: Lower Senonian. 
METATISSOTIA n. gen. Hyatt. 
Following out the system adopted in these pages, it becomes obvious 
that species having the peculiar development of Metatissotia fourneli and 
robini can not be associated with either Tissotia or Subtissotia. The entire 
ontogeny, including the gerontic stage, of these highly compressed forms 
is distinct from Zissotia and Subtissotia on the one side and from the more 
accelerated development of Paratissotia on the other. 
The typical ontogeny begins with a stage having a compressed smooth 
form and a continuous keel. In the next stage there is a more or less trun- 
cated venter having also a continuous keel, but with nodes at the termination 
of costee that appear on the sides, and nodes also on the umbilical shoulders. 
In the gerontic stage, the cost, keel, and channels finally disppear, leaving 
the sides smooth or ornamented only with large nodes, and the venter more 
or less angular. 
MeraTissoTia FOURNELI (Bayle). 
Buchiceras fourneli Bayle, 1878, Expl. de la Carte géol. France, Vol. IV, pl. 40, 
fig. 3 (not fig. 4). 
Tissotia fourneli Peron, 1890, Moll. Crét. de la Tunisie, pl. 15, figs. 10-14. 
Tissotia fourneli Peron, 1897, Mém. Soc. géol. France, Paléontologie, Vol. VII, No. 
iLife Yolls al(0) 
The development has been determined by Peron in his Ammonites de 
lAlgérie, cited above. In the figures of his youngest specimen, which 
measures about 30 mm. in diameter, there are large dichotomous cost 
with alternating short single costze. In the oldest part of this specimen and in 
