199 PALAEONTOLOGY OF NEW-YORK. 



Cexus ASPIDOCRINVS ( n. g.). 



[ Gr. oo'vi;, scutum ; xpivoi, lilium.'] 



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 

 pl&tes. 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. 



Aspidocrinns scntelliforniis ( 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 imknown. Point of attachment small, circular. 



These bases of this species of Aspidocrinus are extremely abundant in the upper 

 part of the shaly 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. 



