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1883, ] 83 (Williams, 
When the spines are preserved in relation to the vault, although the 
Specimen was crushed and thrown out of normal shape, the vaglt plates 
and their spines were held together during the process of fossilization. 
The evidence is such as to suggest that the spines were united to the 
plates by a tough ligamentous attachment which withstood decomposition 
long after the fossil was buried. 
The calyx plates were thin and frequently occur detached, but the basal 
plates were thickened toward the center of the disk where they joined the 
column, and were generally preserved together, though separate from the 
test of the calyx. 
In studying this genus, I have examined several specimens which agree 
with the typical form in the general character of the plates and the arms in 
One case, and possess the pitted tubercles on the surface. 
The most important among these is the original specimen of a figure is- 
Sued by the New York State Museum with the name Platycrinus? puncto- 
brachiatus. 
The original is in the Museum of Cornell University. The name was 
Proposed by Prof. Hall, but, as he informs me, the species was never de- 
Scribed. his, with several other undescribed species, was photographed 
and the plate was privately distributed abut 1872, with names attached, 
but with no descriptions. The arms, the shape of calyx, and the plates 
that were preserved, correspond in general with the A. Jthacensis, but the 
tubercles on the calyx plates are finer, more numerous, and the pitting 
very indistinct, and the basal plates are relatively larger than in the typi- 
Cal specimens of that species. Hence we are led to believe that the Ham- 
ilton species is distinct from the Chemung specimens, and even if it were 
Properly described and published, it is probably safe to regard it as a 
distinct species. Although the specimen shows no traces of the free 
Spines, the nature of the tubercles leave little doubt of a generic identity 
With Arthroacantha Ithacensis, and the Hamilton form may be called Ar- 
hroacantha punctobrachiata. 
In the Museum of Cornell University are two specimens, each a portion 
of the bagal disc, which appear to be identical with A. punctobrachiatus. 
One is marked Moscow shale, locality not designated ; the other is marked 
Hamilton Period, Delphi, N. Y., and is on a soft dark shale with specimens 
of Pholidops. 
Another specimen, generically identical, but too imperfect for specific 
determination, is in the collection of Prof. 8. G. Williams, from the Hamil- 
ton gsroup at Ensinore Glen, Owasco lake, N. Y. 
Dr, Charles Wachsmuth of Burlington, Iowa, informs me of having ex- 
'mined specimens of apparently the same species, said to have come from 
Hamilton group, Ontario, Canada. 
A Single calyx plate from High-point, Ontario Co., N. Y., has large, 
Coarse tubercles, and the plate is evidently from a much larger specimen 
than any seen at Ithaca, or in the Hamilton group, it is probably a dis- 
tinct Species, 
