17® 
PALAEONTOLOGY OF NEW-YORK. 
T This species is distinguished by the prominent and rather distant spiniferous 
tubercles, by the shallow median depression of the ventral valve, and also, by the 
strong curving spines on the cardino-lateral margins. In an examination of twenty 
or thirty individuals of this species, I am unable to find any variations or grada¬ 
tions that would indicate an approach to any other species. The shell appears to 
have been very variable in form in its normal Condition, and this variation has 
been increased by pressure during the consolidation of the matrix. The form of 
the valves .does not vary greatly from those of P. hirsutus, but it is usually pro¬ 
portionally shorter on the hinge-line. 
The specimens, though occurring in considerable numbers, have not afforded 
satisfactory means of determining the character of the hinge, or the presence or 
absence of an-area. 
Geological formation and locality. In the Chemung group at Philipsburgh in 
Allegany county, and near Elmira. 
Productella rarispina. 
PLATE XXIV. 
Produdus rarispinus : Hall in Tenth Report on the State Cabinet, p. 178. 1857. 
Shell semielliptical; the proportions of length and breadth as 6 to 8, 
as 7 to 10, or sometimes equal; hinge-line equalling or a little greater 
than the width of the shell. 
Ventral valve ventricose, somewhat flattened or slightly depressed in 
the middle, curving abruptly to the front, and a little more gradually 
to the baso-iateral margins, abruptly depressed on the cardino-lateral 
slopes and expanded into ears which are strongly deflected at fhe 
extremities. 
Dorsal valve deeply concave in the middle, flattened or slightly concave 
on the cardinal angles. 
Surface marked by fine concentric striae, and sometimes, in partially 
exfoliated shells, there are appearances of radiating striae. The ears 
are strongly wrinkled, and support several comparatively strong round¬ 
ed spines, and others of similar character are scattered over the sur¬ 
face. These spines rise directly from the shell, with a pustule-like 
elevation on all sides, but not raised in elongate nodes as in most of 
the species. The dorsal valve also bears marks of a few similar spines. 
