ORISKANY SANDSTONE. 4«3 



The species which I have grouped under this designation, have, in some 

 of their forms, been described as Terebratula, Atrypa and Pentamerus, 

 and more recently I have referred them to Meganteeis ; to neither of 

 which genera do they belong. One of the most common species in the 

 Oriskany sandstone attracted attention in the collections which were made 

 at the Helderberg mountains forty years ago, and specimens are preserved 

 in the " Clinton Collection " of the Albany Institute. Prof. Amos Eaton, 

 in his Geological Textbook published in 1832 (page 45), recognizes two 

 species which he notices as Terebratula ovoides and T. perovalis ; but since 

 he remarks that they are found "also in all parts of Europe in the same 

 rock," it is to be presumed that he regarded these forms as identical with 

 the European species of the same names. 



In 1839, Mr. Conrau described the more common form from the Ori- 

 skany sandstone as Atrypa elongata*; a name adopted by the geologists of 

 New- York, and perpetuated in their reports. He also describes a species 

 of that genus, from the Lower Helderberg group, as Atrypa aquiradiataf. 



In 1843, Mr. Vanuxem described a species of this genus, from the Upper 

 Helderberg limestone, as Pentamerus elongata\. 



These fossils, though presenting considerable variety when compared 

 in their extreme forms, nevertheless constitute a very natural and beauti- 

 ful group, easily recognized both in their external and internal characters||. 



* Annual Report on the Paleontology of New-York, 1839, p. 65. 



t Journal of the Academy of Natural Sciences, Vol. viii, 1842, p. 266. 



X Geological Report of the Third District of New-York, 1848, pp.182 & 183, f. 1. 



'll In 185.5, after having studied the exterior of the shell and its structure, together with the casts wliich 

 I had obtained in New-York, I proposed for these fo.ssiIs a distinct generic designation; but receiving soon 

 afterwards, Mr. DAViDgoii's paper "On the system.itic .irrangenient of recent and fo.ssil brachiopoda " 

 published in the Annals and Magazine of Natural History for December 1855, I observed for the first time, 

 in the accompanying improved table of genera, the name of Meganterit (Sdess), with a reference to Tere- 

 bratula archiaci as the type of the genus. Tlie figure given in the Palaeontographica so much resembles the 

 casts of some of the Uensselajria;, that I inferred the two to be identical, and have thus described these 

 fossils in my paper published in the Regents' Report for 18.50 ( Palaiozoic Fo.ssils, 1857) ; and it was not 

 until recently (1858) that my correspondence with Mr. Davidson and Mr. Sue«s, and the reception of the 

 paper of 31r. Si'E.ss on the Genus Meqanteris, with illustrations, has satisfied me that this genus is quite 

 distinct from the Rensseljebia. 



