METOICOCERATID 2. 125 
that the sutures on the two sides differed considerably. They were alike 
in their first and second lateral lobes and saddles, but the third lateral 
saddles were simpler on the right side, the side given in Pl. XIII, fig. 4, in 
having the marginals less distinct and the fourth lateral was entire instead 
of being bifid. The outlines internally were the same and there were 
seven saddles and seven lobes on each side, and saddles at the lines of 
involution. The differences between the more fully developed sutures 
on the left side, those of the right, and the oldest suture showed similar 
degenerations, the saddles becoming much shorter and broader in propor- 
tion and the marginals less distinct. 
The table on page 126 gives an account of the variations observed 
in the sutures. It will be observed that the first lateral lobe is quite 
generally bifid, but in the largest specimen (Pl. XIV, fig. 8) from Elm 
Fork, Tex., it is sometimes trifid. It is very obvious that this character- 
istic may be capable of two translations, some of the first lateral lobes in 
this specimen being made trifid by a slight enlargement and extension of 
the main terminal marginal lobe. 
The second lateral lobe varies from simple primitive form of bifidity 
to trifid without regard to age, but in most specimens it is bifid. The third 
lateral saddle is bifid or trifid without regard to age, but tends to become 
quadrifid in older stages. The fourth varies from entire to bifid or trifid, 
but in most cases is bifid or trifid. The fifth varies from entire to bifid or 
trifid, but is in most cases entire, sometimes bifid but rarely trifid. The 
number of lobes and saddles on the sides varies from 11 to 14 in the early 
ephebic substages and from 13 to 16 in the full grown. 
No. 6 is taken from a fossil with a notably stouter volution, more 
prominent coarser costz, and larger tubercles than any of its companions 
of the same size from the same locality, Elm Fork, Tex The whole 
diameter of this fossil when complete was probably not less than 63 mm. 
and the living chamber of the usual length, a little over half of a volution. 
Unluckily, like all others of this species, the aperture has been badly 
broken and the rostrum could not be observed. I at first thought this 
exceptionally stout and more coarsely ornamented specimen must be a 
different species, but the sutures, when laid bare, were identical with 
others here described as M. whitei, especially close to that given on Pl 
XIV, fig. 10. 
