ENGONOCERATID®. 169 
’ 
the ephebic stage, becomes broader and slightly rounded, but still retains 
the tubercles and asymmetrical aspect due to their prominence and alter- 
nation. The gerontic living chamber is about one-half of a volution in 
length on the ventral side, the dorsal side being absent. 
The earliest suture in type No. 431 at diameter of 26 mm. from line 
of involution to venter has eight saddles and seven lobes to the umbilical 
shoulders. Beyond this they were not visible. The saddles are narrow 
and phylliform or club shaped; the lobes also are clubbed and have primi- 
tive denticulations. First lateral saddle is trifid and inner marginal lobe is 
digitated, the second to fourth entire, fifth to eighth bifid. The ventral 
lobe is longer than usual in this genus, but has the usual form, divided by 
entire broad siphonal saddle. The first, second, and third laterals have 
about five denticulations unequally divided, and the fourth is trifid. Later 
in the gerontic stage the second to fourth saddles become either bifid or 
have more digitations, and the digitations of the lobes increase to seven; 
the phylliform aspect also increases. 
When the volution is about 37 mm. in diameter from line of involution 
to venter, there are apparently about the same number of saddles and 
lobes, Pl. XXI, fig. 5. The lobes have more denticulations and the third 
saddles are also faintly bifid. In another specimen, Pl. XXI, fig. 6, same 
locality at about the same age, all the saddles and lobes are shorter and 
broader in proportion, but decidedly phylliform, the lobes are more denticu- 
lated, the first lateral saddles deeply trifid, the second to fifth saddles entire, 
the sixth to the eighth (the last one visible) distinctly bifid. 
A cast (No. 10755, Boston Society of Natural History) from Bell County, 
Tex., is 75 mm. in whole diameter. The entire volution is 39 mm. from 
venter to line of involution; the umbilicus is 10 mm.; the diameter oppo- 
site from line of involution to venter is 27 mm. 
This is in the gerontic stage, the last five sutures overlapping. There 
are ten saddles and nine lobes on the left side. The second to the sixth 
are entire, the seventh to the ninth are bifid, and the tenth is entire. The 
saddles and lobes have the elongated phylliform character of this species. 
Locality: Gabriel, Williamson County, Tex. 
Age: Comanche series, Washita? 
The remarkable and highly instructive specimen described below is a 
cast with an approximate diameter of 55 mm. It was received from Dr. 
