388 On Lingidasma^ Etc. — Ulrich. 
posterior border of the brachial valve (fig. 5, «), will probably 
prove an homologous feature. 
Another point of agreement with the trimerellids is fur- 
nished by the archlet. This is represented, in the brachial 
valve, by a faintly impressed semi-circular line in front of the 
platform. (See fig. 5.) 
In the specimen from which the gutta-percha moulds were 
taken, the posterior extremity of the pedicle valve is, unfor- 
tunately, broken away, so that we cannot say positively 
whether an area was present or not. One thing, however, 
seems certain, namely, that only a small portion of deltidium 
projected beyond the border of the opposite valve, and, conse- 
quently, that the larger part of it was internal. This, very 
likely, would be a unique condition, and, as I am not prepared 
to explain the anomaly, the safest policy, manifestly, is to let 
it rest with the bare statement of the apparent fact. 
There yet remain several points in the internal structure of 
the genus which might be discussed, but as they are either not 
understood or deemed of only trivial importance, it would 
not, perhaps be wise to do so. It may be well, however, to 
recommend a careful study of figs. 5, 5 a and 5 c as they repre- 
sent every feature seen on the fossil. 
The remarkable agreement in the character of the platforms 
and in the disposition of the muscular scars above shown to 
exist between the Trimerellidoe and Lingulasma, naturally 
suggests placing the genus in that family. But, as is stated 
at the beginning of this discussion, that could not be done 
without violating what appear to be closer ties. The grounds 
upon which I base my objections to such an allocation are 
(1) that, though the interior of Lingulasma may be said to be 
practically identical with that of the trimerellids, it is still true 
that the muscular systems of both are not materially different 
from that of the Zm^wZ*6?<Te ; and, coupling this fact with (2) 
the linguloid form of the shell of Lingulasma^ and (3) the 
corneo-phosphatic instead of calcareous composition of its 
substance, we have an array of evidence strongly in favor of 
the LinguUdce. Moreover, I am inclined to believe that the 
platforms of Lingulasma schuoherti are exceptionally devel- 
oped and that its trimerellid characters, if the expression be 
allowed, will not prove so marked in other species. 
The position of Lingulasma appears therefore to be dis- 
