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PALAEONTOLOGY OP NEW-YORK. 
CrEMJS Aspidocrinus ( n. g.). 
[ Gr. omjYi£, scutum ; xpivog, h'lium.] 
Base broadly circular, depressed hemispheric or scutelliform : upper 
margins plain or plicate exteriorly; the articulating edges irregular. 
Radial plates and arms unknown. Point of attachment for column 
distinct, small. 
The specimens referred to this genus present themselves as broad scutelliform 
bases of crinoids, or sometimes nearly hemispheric in form. The margins, sometimes 
plain, at others irregular, present but doubtful surfaces of attachment for succeeding 
plates. In one or two individuals, I have observed depressions in the upper margins 
similar to those of Edriocrinus pocilliformis, which would indicate at least ten or 
twelve radial and interradial plates; but no specimen has yet been seen, retaining 
any of the second range of plates. There are many analogies between this form and 
the bases of Edriocrinus ; but the conspicuous mark of attachment for the column, 
and the indication of numerous plates in the second series, preclude the union of 
the two in a single genus. 
Aspidocrinus scutelliformis (n. s.). 
Plate V. Fig. 15 - 18. 
Base scutelliform, concavo-convex, depressed hemispheric : exterior 
smooth or finely granulate; interior smooth. Radial plates and arms 
unknown. 
Column unknown. Point of attachment small, circular. 
These bases of this species of Aspidocrinus are extremely abundant in the upper 
part of the slialy limestone of the Lower Helderberg group, and sometimes form by 
themselves mainly, and with other fragments of crinoids, a stratum which, from the 
abundance of these forms, was originally designated, in the Annual Geological Reports 
of New-York, as the “ Scutella limestone.” This rock is so filled with these remains, 
that many thousands may be counted in the space of a few yards; and the other 
portions of the rock are made up in great measure of these broken cups and other 
crinoidal remains. In some parts of the rock they become rare, and in its western 
and northwestern extension are at present unknown. Although fragments of un¬ 
determined columns are abundant in the formation, I have not thus far been able 
to identify any of them as belonging to this species. 
