16 
MUSEUM BULLETIN No. 31. 
Dalmanella whitiaheri sp. nov. 
Plate V, figures 11-14. 
.Shell large for the genus, plano-convex, wider than long, wide 
at the hinge. The pedicle valve is moderately convex, highest on the 
umbo, and lacks a median ridge. The pedicle valve of young speci- 
mens is only slightly convex. Brachial valve almost absolutely fiat, 
with a slight median groove near the apex. The surface is marked 
by exceedingly fine, thread-like striae which increase rapidly by bifur- 
cation and show a distinct difference in coarseness, there being ten 
or twelve finer striae between a pair lof coarse ones on the front of 
large shells. Interior unknown. 
The largest specimen (used as holotype) is 18 mm. long, 25 mm. 
wide, and the hinge is 22 mm. long (estimated from unbroken half). 
A smaller specimen is 1 2 mm. long, 18 mm. wide, and the width at 
the hinge is 12 mm. This specimen has eight striae in 8 mm. at the 
front and the type has ten in the same interval. 
This species differs from the common D. rogata in its greater 
size, greater width at the hinge, and finer and more numerous striae. 
Beside Dalmanella rogata , three other species are known from the 
Black River and Trenton. Dalmanella Hamburg ensis Walcott is a 
small shell, with few striae. Dalmanella fertilis Bassler has been 
figured but not described. It seems to be very closely allied to D. 
rogata . Dalmanella bassleri Foerste has been described but not 
figured. This species is of the size of D . whittaheri , but according 
to Foerste, the striae are coarse. It is found in the Cynthiana forma- 
tion of Kentucky. 
Horizon and Locality. Found originally in the Prasopora beds 
of the Trenton at Peterborough, Ont., where it is not uncommon. 
Mr, T. H. Clark has more recently (obtained specimens from the middle 
Trenton (280 feet above the base) on Roaring Run, near Martinsburg, 
N.Y. Named for E. J. Whittaker, who with the writer, collected the 
types. 
Dalmanella resupinata sp. nov. 
Plate V, figures 7-10. 
This Dalmanella, at first sight very like D. rogata, differs from 
that species in having a shorter hinge, and hence more nearly circular 
shape, and in lacking both the sinus on the brachial valve, except as 
a faint depression near the beak, and the median ridge on the pedicle 
valve. A remarkable feature, and the one which suggested the name, 
is that in senile individuals there is a shallow sinus developed on the 
front of the pedicle valve, and a corresponding low elevation on the 
