METOICOCERATID 2%. 127 
In all of these specimens the first lateral saddles were of very nearly 
the same general character, decidedly deeply bifid, even in the youngest 
stages recorded, and with both arms subdivided by one or more marginal 
lobes; the second lateral saddles were also complex at all stages observed, 
and one small specimen not recorded in the table, with suture lines on the 
last volution running from 12 to 18 mm., showed the same facts. This has 
bifid first and trifid second lateral lobes, with quadrifid third lateral saddles 
on both sides. A bifid fourth is visible on the right side when the volution 
is less than 12 mm. ‘This same saddle with a bifid base is the only one 
visible in another fossil with a suture line of. about 8 mm. It is evident 
that the law of variation in the sutures is that lobes and saddles increase 
in ‘variability of outlines and in number progressively from the venter 
toward the dorsal lines of involution, the so-called auxiliaries or derivatives 
of the primitive second lateral saddles of the young being far more variable 
than the first lateral saddle. 
Locality: Kanab Valley, Utah; Elm Fork, Dallas County, Tex. 
Age: Colorado epoch. 
METOICOCERAS ACCELERATUM n. sp. Hyatt. 
Pl. XIV, figs. 11-14. 
I at first thought this to be the young of the species described by 
Whiteaves as Placenticeras liardense, but the figures given by him merely 
indicate that the venter had continuous cost across it. The condition of 
his fossils was, however, such that he did not see the venter, and this 
can only be inferred from the lateral aspect as given in his drawings. 
Apparently there were no tubercles on the sides in the full-grown specimen, 
and the umbilicus was about the size of that of M. whitei and not so small 
as in this species. There were no nodes nor prominent costz near the 
umbilical shoulder in this fossil, and the two outer rows of tubercles were 
much less prominent than in the preceding species. The venter in the 
first half of the outer volution resembled that of M. whitei at an earlier age 
on the first quarter of the outer volution of the specimen shown in PI. XIV, 
fiz. 1, but with less decided tubercles, and on the latter half of this volution 
it is changed as the venter is in the old age of M. whitei. That is to say, 
the coste that cross it are prominent and flat, but not channeled nor 
concave. The coste on the sides are not so prominent and coarse as in 
