798 Report or tHe Starz Groroaist. 
ward with a somewhat less curvature than the plate and rises to 
the highest point attained by the latter; the inner surface of this 
process is deeply grooved and at its base it is supported by a 
median septum which extends 
We for one-third the length of the 
Ze valve. There is no tent-shaped 
structure for the support of the 
crura as in Eumerria. 
The spirals have the same 
structure as in Eumerria, and the 
eet Gone OE Eee eae Tes posterior margins of the coils are 
fimbriated. The jugum, also, is 
quite similar to that of Hwmetria Vernewiliana, terminating in 
a long, sharp, retrally directed stem, the posterior edges of the 
lamellz both of the stem and the lateral branches being furnished 
with divergent spinules. The extremity of the stem appears to 
be simple. 
Shell strongly punctate. 
Type, Hustedia Mormoni, Marcou (sp.). 
Distribution. Coal measures. 
Trematospira, Hall. 1859. 
(Plate 38, figs. 1-12.) 
Shells transverse, subequally convex, with median fold and 
sinus on brachial and pedicle-valves respectively. Surface covered 
with radial, coarse or fine, simple or duplicate plications. Hinge- 
line straight, often long; cardinal extremities abruptly rounded ; 
anterior margin sinuate. Umbo of the pedicle-valve incurved, 
its apex truncated by a circular foramen. Beneath it lies the 
delthyrium, which is covered by two short incurved plates, more 
or less closely anchylosed along the median suture, and so greatly 
thickened on their interior surface as to appear continuous with 
the substance of the valve. 
The deltarium does not extend downward much more than one- 
half the distance from the apex to the cardinal margin, leaving 
beneath it a crescentic opening which is occupied by the beak of 
the opposite valve. On either side of the deltarium is a narrow 
50 
‘ * Pa ‘ 7 os 
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