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On 
(oop) 
PALZONTOLOGY OF NEW-YORK. 
198. 2. EDMONDIA SUBTRUNCATA (vn. sp.). 
Pu. XXXIV. Fig. 9; and Pu. XXXV. Fig. 3 a, b,c. 
Dorsal and ventral margins subparallel ; anterior extremity abruptly rounded, extending 
a little beyond the umbo; posterior slope straight, oblique ; umbones moderately elevated, 
with an obtuse prominent ridge extending obliquely backwards, and becoming obsolete 
below ; surface marked by fine concentric lines. 
This species is less gibbous than the following, though it is much expanded below the 
umbones, and the front very obtuse. A single specimen preserves a portion of the shell, 
which is marked by fine striz upon the centre and anterior portion ; while upon the posterior 
slope it presents a few strong subimbricating ridges, which are still marked by the strie. 
In the casts of this species from the crystalline portions of the limestone, these ridges are 
often preserved, while other portions are quite smooth. In such instances, there is no 
evidence of muscular impressions in any part of the specimens. 
Plate xxxiv. fig. 9. A specimen preserving a part of the shell; from the soft limestone at Middleville. 
Plate xxxv. fig. 3 a, 6. Casts of the same in the crystalline limestone at Watertown. 
g. 3 
— fig. 3c. Cast of the same, showing strong imbricating ridges towards the base. 
Position and locality. In the central or higher part of the Trenton limestone at Middle- 
ville, and in the crystalline part of the rock at Watertown. (State Collection.) 
199. 3. EDMONDIA? SUBANGULATA (n. sp.). 
PL. XXXV. Figs. 2 a, b. ; 
Subelliptical, with the anterior narrowed and slightly projecting ; umbones very pro- 
minent, subangular, with an obtusely angular elevation extending thence to the posterior 
ventral margin ; hinge line short, deeply grooved near the margin for the insertion of the 
ligament ; surface nearly smooth, or marked by fine strie which become undulating ridges 
upon the posterior slope. 
This shell has a greater proportional length than the preceding, and there is a distinct 
obtusely angular ridge extending from the umbones nearly to the posterior ventral margin. 
The umbones are more angular than the last, the cardinal line shorter, and the anterior 
margin more extended. 
Fig. 2 a. Left valve of this species. 6. Dorsal view of a single valve. 
Position and locality. In the concretionary lower part of the Trenton limestone at Water- 
town, Jefferson county. ( State Collection.) 
* Many shells, suffering from pressure in the soft shaly rocks, become coated by a thin striated film of shale, marked 
like the “slickensides,” as if the surrounding parts had been moved after partial solidification. In other instances, 
there appears to be a collection of shaly matter in a concretionary form around the shell, haying also a striated surface. 
This aggregation of matter around the tube of the Orthoceras, has been regarded as a portion of the animal petrified ; 
but it happens equally to other shells. 
