LOWER HELDERBERG ROCKS. 99 



CRINOlDEi: AND CYSTIDE^ OF THE LOWER HELDERBERG LLMESTONES AND 



ORISKANY SANDSTONE*. 



Upon the commencement of the engraving for the third volume of the 

 Palaeontology of New- York, not more than five species of Crinoidege and 

 CystideaB were known to occur in these rocks. The great numbers of 

 columns and other fragments of these fossils in certain localities induced 

 a belief that a greater number of species would eventually be found ; and 

 a much larger number of plates was assigned for the illustration of these 

 fossils, than would have been required for those at that time known. 



As the collections have progressed, new species have at intervals been 

 discovered, and also better specimens of those previously known ; so that 

 although the material for the illustration of these families of fossils was 



A. ... 



formerly so meagre, we have now the means of presenting an interesting 

 group. The species and individuals are far from being as numerous as 

 those of the Niagara group ; and while a single crinoid and one cystidean 

 only are of the same type, the remainder present a much wider departure 

 from those, than might have been anticipated from the similarity of the 

 sediments, and the affinities of the brachiopoda, corals, and bryozoa of 

 the two periods. 



Notwithstanding these additions of species in the limestones, there 

 still remain numerous fragments of columns, arms, etc., which are yet 

 unidentified. Some fortunate localities will hereafter, probably, furnish 

 as many more species as we now possess ; and, judging from the limited 

 range of most of the known species, we may anticipate a greatly in- 

 creased number, when the formation shall have been thoroughly studied 

 from its best known localities in New- York, along its line of outcrop to 

 the southwest as far as Middle Tennessee. 



* CoBAU AND Brtozoa OF THE LowER Helderberq LIMESTONES. The conspicuous Corals of this period 

 consist <i{ Streptelatma, Zaphrcntis, Favosites, Stromatopora, Chatetes, etc.; while the Bryozoans present 

 numerous forma of Fenatella, Trematopora, Callopora, etc., which closely resemble Niagara species. 

 Conceiving that it would be more satisfactory to publish the Corals and Bryozoa of this and the succeeding 

 groups of str.-»ta altogether, I have made arrangements to give the descriptions and figures of all these in 

 the last volume of the Palaeontology of New-York. 



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