ORDOVICIAN FAUNAS. 125 
it is quite possible that the two species should be considered as the 
same, but the New Jersey specimens seem to differ from that species 
in being less nearly subcircular and in having a proportionally longer 
hinge-line. 
This species occurs most abundantly in a stratum a few feet above 
that containing Jllanurus columbiana, where it is not associated with 
any other species, except a minute, coiled shell, a single, imperfect 
specimen of which has been observed. 
DALMANELLA ELECTRA (Bill.). 
Plate IV., Fig. 138. 
1862. Orthis electra Billings, Pal. Foss., vol. I., p. 79, fig. ¥2. 
Description.—Shell wider than long, subquadrangular or subellipti- 
eal in outline, the hinge-line a little shorter than the greatest width, 
cardinal extremities angular. Pedicle valve moderately convex on 
the umbo, slightly flattened towards the cardinal extremities; the 
beak projecting somewhat beyond the cardinal margin; cardinal area 
narrow, concave above. Brachial valve not seen. Surface marked 
by about fifty fine, subequal, radiating coste, which increase by 
bifurcation. 
The dimensions of a nearly perfect pedicle valve are: length, 5.75 
mm.; width, 7 mm. 
Remarks.—This species is not so abundant as the last, and the only 
specimens observed occur in the bed with ///@nurus, near Columbia. 
The species may be distinguished from D. wemplev by its finer strie, 
which do not alternate in size, and by its less convex pedicle valve, 
which is slightly flattened toward the cardinal angles. 
