108 PSEUDOCERATITES OF THE CRETACEOUS. 
PEDIOCERAS Gerhardt 
Type Ped. cundinamarce, Gerhardt Kreideformation in Columbien, ete. 
Neues Jahrb. fiir Min., Geol., und Pal., Beil.-Bd. 11, 1897-98, p. 172, pl. 4, 
fig. 7. Age Aptian. <A stout, quadragonal, very discoidal shell, with two 
lines of outer tubercles and one on the umbilical shoulders, all very slight, 
coste linear, but prominent on the sides and crossing the venter, which 
is broad and concave. The dorsal side barely covers the outer line of 
tubercles. No sutures given. Includes caquesensis and ubaquensis Karst. 
DOUVILLEICERAS Grossouvre. 
The type of this genus is the fossil figured first by Walch in the 
Naturtorscher, Vol. I, 1774, p. 196, pl. 2, fig. 3. This was cited by Schlotheim 
in his Beitrage zur Naturgeschichte der Versteinerungen in Taschenbuch fiir 
Mineralogie, Jahr. 7, I, p.111, as the type of Amm. mammillatus. The figure 
given by Walch seems to apply to the young of the form usually cited by 
authors as mammillaris and figured by d’Orbigny under this revised name. 
Mammillaris is cited by Grossouvre, without an authority after the name, 
as the type of his genus Dowvilleiceras in his Ammonites de la Craie 
Supérieure, page 26, and the suture alone is given on page 23. 
The young of the shells in the genus have after the smooth nepionic 
stage highly coronate depressed volutions with broad smooth venter and 
a line of spines on the ventro-lateral angles. These are at this time 
coincident with the umbilical shoulders, the true sides of lateral zones being 
of later age. The umbilical zones at this time are broad and smooth and 
convex, reaching from the tubercles to the lines of involution. Faint costze 
are developed from the tubercles in both directions, completely crossing 
the venter, and shorter ones on the sides. They appear also to be dich- 
otomous at the tubercles. Later these large tubercles separate more widely 
and intermediate costae begin to appear, apparently through arrested devel- 
opment of some of the tuberculated cost already existing. These have the 
same form and tubercles, but are less prominent than those on either side 
of them, and sometimes this is carried to the extent of suppressing entirely 
the alternate pairs of tubercles. During this stage the lines of ventral 
tubercles appear, and those may be, but are not always, smaller on the 
alternating coste. Subsequently at some stage the smaller coste and 
tubercles become of equal size with the others. The stage with four lines 
of tubercles may persist until the shell is one-half to five-eighths of an inch 
