SPHENODISCID 4. 81 
are twelve saddles on the side and there may have been one more. The 
first four lateral saddles are similar to those of lenticularis, but are succeeded 
internally by more pairs of divided saddles, and the dorsal lobes and saddles 
differ. he first to the third are quadrifid; the fourth is of same type, but 
has three marginals on the outer arm; the fifth to the seventh are simply 
bifid; the eighth is entire; the ninth is bifid; the tenth and eleventh are 
entire and phylliform. The lobes are all symmetrically bifid, the branches 
subdivided and serrated, but the bases between saddles are entire on both 
sides; even the eleventh lobe is bifid and has minute serrations, and all the 
smaller internal lobes are short and broad. There are ten narrow phylli- 
form dorsal saddles with entire bases in the zone of involution, and prob- 
ably there were originally eleven. The lobes are broad, bifid, and digitated 
like the opposite external ones; the saddles alone are quite different. The 
first dorsals are very narrow, almost linear, and the dorsal lobes are bifid, 
narrow, and long, overlapping as in other species of this genus. I hesitate 
to describe this as a distinct species, because it is a fragment, but its sutures 
can not be reconciled with those of any other species. 
The side, as shown in PI. VI, fig. 4, is evenly convex as in S. stantoni. 
A specimen from the friable marls 3 miles northeast of Ripley, Miss., 
accompanied a specimen described above as S. lenticularis var. mississippi- 
ensis. It was from 75 to 80 mm. in diameter probably when complete. It 
is covered with nacre, but the sutures can be seen sufficiently. At a stage 
when the side is 35 mm. in breadth the sutures have the complex aspect of 
this species in the first four saddles and lobes, the fifth to the seventh are 
bifid on both sides, and there are about eight more entire saddles. This 
specimen appears at first to be identical with the var. mississippiensis from 
the same locality, but while the external aspect is the same the suture line, 
even at this comparatively early age, is like that of beecheri. 
A very fine cast from Mount Wahallak, Kemper County, Miss., col- 
lected by Frederick Braun, of Brooklyn, in arenaceous rock in lower part 
of the Rotten limestone, shows the sutures perfectly and also the inner part 
of the living chamber. The latter is one-half of a volution in length. 
The suture shows eight divided saddles on each side and the form 
and aspect are like those of this species. This fossil has folds on the 
outer half of the outer volution, the inner part being smooth and the sides 
evenly convex. Whole diameter, partly estimated, is 145 mm.; the diameter 
6 
MON XLIV—03 
