36 PALEONTOLOGY OF NEW YORK. 



■ ions. The pygidium of this species, as already noticed, i.s subject to 

 some variation in the matter of surface ornament. The type specimen of Bal- 

 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 

 Ohioi isis, described by Mr. Meek, from the Corniferous limestone of Marblehead, 

 Ohio. In general form and outline, spinose margin and number of annula- 

 tions, D. aspedans presents a close agreement with D. mijrmecophorus. There 

 are however persistent differences in the two species which may be enumerated 

 as follows: in I), aspedans the posterior border between the marginal spines 

 bears no tubercles, and is only slightly elevated; the tubercles of the surface 

 are not oodiform, 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. Rept. 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. 1). 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 lew scattered tubercles; it retains, however, features 

 characteristic of D. Helena (= aspedans) in the regular arrangement of the 

 tubercles upon the aimulat ions, and the absence of an elevated spinose border. 

 It seems advisable to include this slight variation under the species D. aspedans 

 rather than to establish varietal terms for all intermediate forms between the 

 closely allied species I), iisjieelans and I), mi/rmecophorus. The specific name 

 ticulatus has actual priority by a single page over the term aspedans; as, how- 

 ever, the fragmenl designated by the former name proves not to be in all 

 respects a normal example of the species it represents, and as the description 



