ENGONOCERATID 2t. 185 
by Professor Cragin, shows the subacute venter. he eighth saddles are 
bifid in this fragment and there are only ten on the right side, with large 
unequally bifid first laterals as in large fragment described above. 
Locality: Fifteen miles west of Denison, Tex. Locality 1492, U.S. 
Geological Survey. 
Age: Fredericksburg group of Comanche series. 
One fragment is 55 mm. from line of involution to venter without the 
shell. he first lateral saddle is deeply bifid, and, counting this as one, 
there are only five entire saddles, some of which, probably owing to wear, 
appear to show a faint tendency to become bifid. The sixth to the ninth 
saddles are distinctly bifid; the tenth is a very broad saddle with three 
minute marginal lobes, and the eleventh is another broad saddle which is 
entire to the line of involution. On the opposite or right side the broad 
tenth saddle is divided into two bifid saddles, so that there are obviously 
twelve on that side. 
Locality: Cow Creek, Travis County, Tex. No. 19105, U.S. National 
Museum. 
METENGONOCERAS AMBIGUUM n. sp. Hyatt. 
Pl. XXVI, figs. 5-7. 
One nearly entire cast of this form is 79 mm. in diameter, the last 
volution 44 mm. from line of involution to venter, the umbilicus 6 mm., and 
the opposite part of volution 29 mm. The greatest transverse diameter 
through median surface is 17 mm. and is somewhat less than in a perfect 
specimen. : 
The sutures have smaller saddles than at the same age in M. inseriptum, 
are also less distant throughout, become still more approximate in later 
stages, and are straighter. There are thirty septa in this specimen to twenty- 
four in inscriptum at same diameter. The sixth saddles were bifid on both 
sides. 
Fold-like costz along the inner part of the volution are plainly visible 
and there are small nodes along the ventro-lateral angles, the venter being 
here famtly sinuous. The venter was much eroded, but in two places it 
showed a narrowly rounded area and on the end of this volution is subacute. 
Excavation was not very successful and I could only demonstrate that the 
venter was extremely narrow in the ephebic stage and perhaps not distinct 
from that of Eng. inscriptum at the same age. 
