On Lingulasma , Etc .— Ulrich. 
387 
were thinner and contained a smaller percentage of calcareous 
matter than the shells of those other genera. 
In the brachial valve of Dinobolus we have a rather strong¬ 
ly marked sub-cardinal scar situated in the umbonal cavity. 
This scar is represented by the convex triangular space 
marked b in figure 5. In most species of Dinobolus this part 
is impressed, but in D. transversus Salter, it is elevated and 
of triangular form as in Lingulasma . In front of this Dino¬ 
bolus has a large sub-rhomboidal post-median scar, with a 
longitudinal median keel in at least two species (D. trans¬ 
versus and davidsoni Salter.) This scar is represented in 
fig. 5, at p. Directly in front of it is the faintly traceable 
median pair, the same again as in Lingulasma (fig. 5, atm), 
and, on each side of these, one of the well-marked laterals. 
The last scars seem to diverge posteriorly in Dinobolus while 
they converge in the same direction in Lingulasma. If, how¬ 
ever, the parallel lines marking the surface of the scars be com¬ 
pared it will be seen that they, at any rate, run in the same di¬ 
rection in both. The anteriors are not readily determined in 
Lingulasma , yet it is scarcely to be questioned that they were 
placed, as in the trimerellids generally, at the center of the 
anterior extremity of the platform. 
Lingulasma has two other sets of scars which appear to be 
homologues of two pairs found in the trimerellids: viz., the 
umbo-laterals and transverse scars of Davidson and King. 
In Trimerella and Monomerella the umbo-laterals are situ¬ 
ated very near the “ crescent,” but in Dinobolus they are 
placed close to the sub-cardinals and post-medians. Thus, 
that genus again agrees with Lingulasma (fig. 5, n). The 
transverse scars (at any rate the impressions which I have 
identified with them) occupy positions in the valves of Lingu¬ 
lasma much nearer their sides than is the case in any of the 
trimerellids. This difference, however, is largely accounted 
for by the comparatively greater width of the platform and 
the elongate form of the valves. 
Concerning the crescent , which seems to be one of the most 
persistent characters of the Trimerellidce , I cannot say that it 
is unequivocally represented in Lingulasma. In the pedicle 
valve, at least, I have not found anything that might be re¬ 
ferred to it; but the small transverse ridge just within the 
