36 
PALEONTOLOGY OF NEW YORK. 
Observations. The pygidium of this species, as already noticed, is subject to 
some variation in the matter of surface ornament. The type specimen of Dal- 
manites Helena is from the Corniferous limestone of the Falls of the Ohio, and 
all specimens from this locality have shown a regularly tubercled surface. In 
the limestones of the same age near LeRoy, N. Y., where the species is abun¬ 
dantly represented, the ornamentation has become nearly obsolete, and it is 
probable that a specimen in such condition was the original of the Dalmanites 
Ohioensis, described by Mr. Meek, from the Corniferous limestone of Marblehead, 
Ohio. In general form and outline, spinose margin and number of annula- 
tions, D. aspectans presents a close agreement with D. myrmecophorus. There 
are however persistent differences in the two species which may be enumerated 
as follows; in D. aspectans the posterior border between the marginal spines 
bears no tubercles, and is only slightly elevated; the tubercles of the surface 
are not nodiform, and are always regularly arranged, except upon the lateral 
margins; the terminal spines are short and not laterally flattened. The 
original of Asaphus? denticulatus, Conrad (Fifth Ann. Kept. Pal. N. Y., p. 68. 
1841), was a fragment of a pygidium reported as from the Schoharie grit, at 
Schoharie, and a specimen from the Upper Helderberg limestone at Schoharie, 
exhibiting the same characters as those accredited to Mr. Conrad’s type, was 
figured in the Illustrations of Devonian Fossils (pi. x, fig. I). The original 
of Mr. Conrad’s description is no longer accessible, but the specimen mentioned 
from the limestone shows a variation from the type of Dalmanites Helena in 
having the posterior spines broader, stouter and more flattened vertically, the 
posterior border bearing a few scattered tubercles; it retains, however, features 
characteristic of D. Helena (= aspectans) in the regular arrangement of the 
tubercles upon the annulations, and the absence of an elevated spinose border. 
It seems advisable to include this slight variation under the species D. aspectans 
rather than to establish varietal terms for all intermediate forms between the 
closely allied species D. aspectans and D. myrmecophorus. The specific name 
denticulatus has actual priority by a single page over the term aspectans; as, how¬ 
ever, the fragment designated by the former name proves not to be in all 
respects a normal example of the species it represents, and as the description 
