SPHENODISCID 4. a 
the other rows to the venter have the elongated aspect of the ephebic 
sutures of this variety. The outer or first laterals are slightly more distant 
from the lobes than in the ephebice substage, but the second, third, fourth, 
fifth, and sixth laterals overlap the lobes more than in that stage. The con- 
tour of the venter and aspect of the sutures do not indicate advanced age. 
The largest fragment was probably only in the parephebic or anagerontic 
substage and must have belonged to a much larger shell. 
Mr. Stanton has kindly sent me a tracing of a suture from a large 
specimen which he supposes is the one that furnished the suture figured 
by Meek on pl. 34. This suture has attenuated saddles and lobes more 
like those of var. splendens than the typical lenticularis. 
Locality : South Dakota. 
Age: Fox Hills group, Upper Cretaceous. 
SPHENODISCUS LENTICULARIS variety MISSISSIPPIENSIS Hyatt. 
Pl. IX, figs. 7-9. 
There are two more or less crushed specimens in the National Museum 
from friable marls on Owl Creek, 3 miles northeast of Ripley, Miss., 
No 20863. These have smooth shells, except for well-defined bands of 
growth, and evenly convex sides and sutures that are more like those 
of lenticularis than those of any other species. The lobes and saddles are 
remarkably long and similar, and although the ventral saddles are different, 
they are not widely different. The largest fragment, belonging to a fossil 
probably about 200 mm. in diameter, has only five columns of divided 
saddles on the right side (PL IX, figs. 7, 8). The actual breadth of the side 
where this suture was studied is 111 mm. he dorsal saddles are remark- 
ably unsymmetrical, and these and the antisiphonal lobes are different 
from those of the western variety splendens, and further investigations 
may show these to be distinct, but the materials do not seem at present 
10 justify a separation. The suture of the smaller specimen (PI. IX, fig. 9), 
taken where the side was about 78 mm. broad, agrees, considering the 
difference of age, nearly enough with that of the preceding to be placed 
in the same variety, but the dorsals were not seen. This cast is identical 
with that shell in external aspect and has the shell partly preserved on one 
side. This has the usual brilliantly nacreous layers, and what seems to be 
