386 
On Lingulasma , Etc .— Ulrich. 
it is true, these are separated by a third convex longitudinal 
space, causing the platform to appear tri-lobed. But little im¬ 
portance, however, can be attached to this difference, since tri- 
lobed platforms pertain to unquestioned trimerellids, the 
median lobe evidently representing only a greater develop¬ 
ment of the median plate which, in Trimerella , supports the 
platform and divides the space beneath it into two tunnel-like 
vaults. Even these vaults, which are not always present in 
Trimerella and not at all in Mohomerella and Dinobolus , are 
represented in Lingulasma. 
The cast of the interior which furnished the guttapercha 
squeezes represented by fig. 5 and 5 a, originally preserved 
much of the shell and all of that pertaining to the platform. 
This was carefully removed and during the process it was 
noticed that the platform consisted of numerous cup¬ 
shaped laminae placed within one another and so that an open 
space was left between each and the preceding and succeeding 
ones. From this it is evident that the vaults, of which in this 
specimen the last are only deeply concave spaces beneath the 
front of the platform, were closed at intervals. The develop¬ 
ment of these plates I can explain only by supposing them to 
have been intended to act as supports to the platform. That 
they were not complete is evidenced by the fact that some of 
the surrounding matrix had entered into the cavities men¬ 
tioned. Indeed, in two casts of the interior from Savanah, 
Ill., the matrix completely fills the spaces under the platforms 
to the beaks. 
The resemblances between the Trimerellidce and Lingulas¬ 
ma already pointed out are fully sustained when we compare 
the muscular scars and certain other internal features of, per¬ 
haps, minor importance. In the first place we find that in 
both the platforms are marked by four sets of scars. These 
Davidson and King distinguished by the names, medians , an¬ 
terior s, laterals , and post-medians. The last set those authors 
believed to have no relation to the others. They were in¬ 
clined to refer them to the ovaries. 
In comparing the relative positions of these and other sets 
of scars we find that the correspondence with Dinobolus is 
greater than with either Trimerella or Monomerella. This is 
to be expected, since Dinobolus includes species whose shells 
