PLACENTICERATID &. 217 
aspect but very much simpler in outline than those of P. whitfieldi or even 
these of true placenta at the same age. The perfect venter at this stage is 
concave and it continues smooth and concave in this species until the shell 
is much larger, but then becomes flattened and apparently exactly similar 
to that of true P. placenta, but is broader at the same age and flatter than 
in P. whitfieldi. he sutures are more like those of P. placenta than those of 
P. whitfieldi. The casts do not show the shell except in the young stage 
and this has obscure sigmoidal bands of growth like those in whitfieldi_ but 
no cost on the shell and none on the casts as is usual in that species. 
The youngest stage is more involute than in P. placenta and is like some 
specimens of P. whitfieldi in this respect. 
Stanton’s figure of the suture was taken from the ephebic volution of 
a specimen of the diameter of 173 mm The volutions were perfectly 
smooth on this cast, with a flat, broad venter, and at the diameter given on 
the third quarter of the outer volution the gerontic stage had begun and 
the last part of the volution was helmet-shaped in section with a rounded 
venter. This shows a paragerontic stage earlier than is usual in placenta or 
in whitfieldi. 
The specimen alluded to by Stanton, from Ellis County, Tex., Eagle 
Ford shales or Fort Benton Group, is a cast 171 mm. in diameter, with 
form almost as much compressed, and with thin venter, as in whitfieldi, but 
the sutures are more like those of stantoni. They are, however, more 
deeply cut, being older than those figured and more like those of whitfieldi. 
In fact, I do not see here nor elsewhere any possibility of drawing 
sharp lines, except between the genera; the species all run into one another. 
Locality: Upper Kanab, Utah; Huerfano Park, Colorado: 
Age: Colorado Epoch, Upper Cretaceous. 
PLACENTICERAS PSEUDOPLACENTA variety OCCIDENTALE Hyatt. 
Pl. XLV, figs. 1, 2. 
The saddles and lobes have the elongated forms of those of P. whit- 
fieldi, but are more solid; the ventral lobe has the same elongated arms, and 
the ventral saddle is also similar, but the lobes and saddles are simpler and 
more like syrtale until a later stage than in P. whitfieldi. The shells have 
a row of tubercles on the umbilical shoulders and fine tubercles on the 
venter. The principal distinction is, however, the breadth of the venter 
