On Lingulasma , Etc .— Ulrich . 385 
of the Lingulidoe , with a strongly marked tendency to assume 
and, perhaps in part foreshadowing, the internal peculiarities 
of the Trimerellidce , a family of paleozoic shells whose charac¬ 
ters have been so conscientiously and admirably worked out by 
the late Mr. Thomas Davidson and Prof. Wm. King. (Quart. 
Jour. Geol. Soc. vol. xxx; 1874.) It should be remarked 
further that their memoir has formed the ground plan upon 
which I based my investigations of Lingulasma , and that 
their provisional designations of the various scars, where the 
equivalence of these could be determined with reasonable cer¬ 
tainty, have been adopted by me in describing the internal 
features of the genus. 
The family Trimerellidce , as defined by Davidson and King, 
includes more or less calcareous, transversely or longitudin¬ 
ally elongated, and both thick and thin shells. We have here 
three features in which Lingulasma does not correspond with 
the family. Of these, the first is, in my estimation, by far the 
most important and, fearing that my intentions may be mis¬ 
understood, I will state at once that I regard the unequivo¬ 
cally corneo-phosphatic shell of Lingulasma as an insurmount¬ 
able obstacle to an arrangement of the genus with the Trimer¬ 
ellidce ; and I may add that in none of its external characters 
does the new genus correspond with the trimerellids being in 
those respects indistinguishable from the lingulids. 
After the above preliminary declarations we may pass di¬ 
rectly to a consideration of the parts belonging strictly to the 
interior. Here, I believe myself capable of showing, what may 
be already obvious to the reader, that, while the internal char¬ 
acters taken as a whole deviate widely from true Lingula , 
they correspond in a great degree with those of the Trimer¬ 
ellidce. 
The most striking feature of the interior of . both valves is 
the elongated region of the posterior halves which has been 
called the platform. With regard to this feature I may safely 
say that in no trimerellid is it better developed than in Lingu¬ 
lasma. On the contrary only in a very few is it nearly as 
large or so much elevated. As usual among them the plat¬ 
form and median plate of the brachial valve of Lingulasma is 
higher than that of the pedicle one. The platform in the lat¬ 
ter also greatly resembles that of the typical species of Trim- 
erella in consisting of two convex divisions. In Lingulasma , 
