36 PSEUDOCERATITES OF THE CRETACEOUS. 
true Tissotia as here defined, but it differs in the more complex outlines of 
the sutures, all of which have small marginal lobes and saddles. In my 
opinion, the genus should be limited, so far as known, to one species, the 
type described by Peron. The other species described under this name are 
obviously widely distinct in their forms and mode of development. The 
sutures resemble those of Roemeroceras ou the lateral aspect. The ventral 
lobes are also alike, so far as can be seen on Peron’s figure. Peron’s sug- 
gestion that these are the ancestors of Tissotia and its allies in the Senonian 
appears to be supported by the facts so far as now known. They appear 
also to have been the immediate ancestors of Hemitissotia and its allies in 
the Senonian, but this last inference needs confirmation that can only be 
obtained through the study of the young of the latter. 
PSEUDOTISSOTIA GALLIENNEI (d’Orbigny). 
Pseudotissotia galliennei Peron, 1896, Mém. Soc. géol. France, Paléontologie, Vol. 
WIL No, Wt, jalle 25 ier, BS joll GB, ines I 
This is a moderately compressed but still comparatively discoidal form, 
with large umbilicus and involution enveloping something more than one- 
half of the sides, according to Peron’s figures. The venter is flattened, 
with heavy, contmuous keel and shallow channels bordered externally by 
thick continuous ridges. The sides have very broad fold-like costae with- 
out tubercles. In extreme age all of these ornaments disappear. The 
entire aspect and genetic transformations of this fossil are so similar to 
those of Tissotia tissoti that it would have to be included in the same genus, 
if the sutures were unknown. 
Locality: France. 
Age: Turonian. 
PSEUDOTISSOTIA ? TUNISIENSIS n. sp. Hyatt. 
Tissotia ct. fourneli Peron, 1896, Mém. Soc. géol. France, Paléontologie, Vol. VI. 
No. 17, pl. 12, figs. 7, 8. 
Tissotia fourneli Peron, 1890, Moll. Crét. de la Tunisie, pl. 17, figs. 11-13. . 
This remarkable fragment has a truncated venter, entire keel, and 
compressed volution, with moderately large umbilicus. The coste are fold- 
like, with tubercles on the umbilical shoulders and a line of closely set 
elongated tubercles on the ventro-lateral angles. The first lateral saddles 
are trifid and rather peculiar, owing to the approximate equality of the three 
