110 PSEUDOCERATITES OF THE CRETACEOUS. 
DovUVILLEICERAS ORBIGNYI n. sp. Hyatt. 
Ammonites mammillaris VOrbigny (pars), 1840, Terr. Crétacé, pl. 73 (not pl. 72). 
Through the neanic stage this species is not separable from mammil- 
lare except by its slightly more discoidal form and more prominent tuber- 
cles on the venter, but later than this the coste separate as given in’ 
dVOrbigny’s figure, through the nondevelopment of intermediate cost. 
This gives an entirely distinct character to the ornamentation. One frag- 
ment from Cherbourg, in the Koninek collection in the Museum of Com- 
parative Zoology, shows perhaps a third species, since this change is much 
more pronounced than in the type cited above and occurs at an earlier age. 
This genus is represented in North America by Douv. (Acanth.) 
spiniferum (Whiteaves), found in Canada, and there seem to be two 
species, the first described in Mesozoic Fossils, Vol. I, pt. 1, pl. 4, and the 
second in the same, pt. 4, pl. 35. The differences appear to le in the 
costations and tubercles of the older stages. 
Localities: Numerous, western Europe. 
Age: Albian. 
SCHLUETERICERAS n. gen. Hyatt. 
This group has in its type species Schluetericeras nodosoides, described 
and figured in Schliiter’s Cephalopoden der oberen deutschen Kreide (p. 18, 
pl. 8, figs. 1-4) a neanic stage with compressed, flat-sided, moderately 
involute shell that resembles the neanic shells of Metoicoceras and Mantelli- 
ceras in aspect and in the possession of six rows of tubercles and a concave, 
keelless venter. In the next stage, however, the ventral lines of tubercles 
are lost, thus reducing the shell to a quadri-tuberculate stage and much 
larger and longer nodes and more prominent single lateral coste are 
developed, while at the same time the venter becomes flatter. This is a 
degenerative, obviously gerontic change, but it is so distinct from the 
similar stages of other genera that it is quite sufficient to characterize the 
group. It is from the Lower Turonian according to Schliiter. 
Other species of this genus are as follows: Schluetericeras vielbanci of 
the Turonian, described and figured by d’Orbigny in Terrain Crétacé : 
(pl. 108) as woolgari, but changed in his Prodrome (Pt. II, p. 189) to this 
