SPHENODISCID A. 69 
The form, surface, etc., are the same as in smaller specimen above 
described. The sutures, however, being much more mature, are quite dis- 
tinct in details of outline, although the general aspects were similar. The 
saddles have the swollen phylliform outlines of the bases and the lobes 
the same spreading tops. The first and second lateral saddles on the 
youngest part of the outer volution are trifid, the third, fourth, and fifth are 
bifid, the remainder are entire and rounded, becoming gradually flattened 
and more depressed toward the lines of involution. This was on the side 
figured, but on the right side there are six columns of divided saddles, the 
sixth having only, however, a very small median marginal. The first 
lateral on this side is bifid, the second trifid, and the four other divided 
saddles are bifid. The first, second, and third lateral lobes present irregu- 
larities that obscure their origin, but are probably from the trifid type; the 
remainder are all distinctly bifid. There are about fourteen saddles beyond 
the fourth, and probably two rows more on the outer part of same volu- 
tion, since the spiral arrangement is well marked and the sharp umbilical 
sides are transformed into flat zones on the last half of this volution. The 
saddles and lobes are more complicated and the first more deeply undercut 
near the end of this volution, but there is no other marked difference pro- 
duced by the development of the shell, except that the saddles are all mark- 
edly longer in proportion and more slender. The rotund, phylliform 
aspect of the bases of the saddles is maintained because of the slow devel- 
opment of the dividing marginal saddles. The sutures are easily separable 
except near the umbilicus. The ventral is a trifle longer than the first 
lateral, and there is a descent from the last to the third lateral, and beyond 
this a decided break owing to the sudden decrease in the fourth lateral, 
which is only one-half the length of the third lateral. The remaining lobes 
and saddles slowly decrease in length. The differences between the third 
and fourth laterals decrease in the older parts of this volution and the 
sutures approximate somewhat, showing the approach of old age. The 
fragment figured by Whitfield” may perhaps be a specimen of this species 
or some related form. Such broad internal saddles and digitate short lobes 
occur in lobatus. They are simpler in outline although belonging to a larger 
specimen than that here described as variety beechert. There are two very 
large specimens in American Museum of Natural History in New York 
«Mon. U.S. Geol. Survey, Vol. XVIII, pl. 41. 
