0 RISK ANY SANDSTONE. 
453 
JlENSSELiERIA. 
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 Meganteris ; 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. Conrab 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 cequiradiata\. 
In 1843, Mr. Yanuxem described a species of this genus, from the Upper 
Helderberg limestone, as Pentamerus elongaia\. 
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 Palaeontology of New-York, 1839, p.65. 
t Journal of the Academy of Natural Sciences, Vol. viii, 1842, p.266. 
$ Geological Report of the Third District of New-York, 1843, pp.182 & 133, f. 1. 
|| In 1855, after having studied the exterior of the shell and its structure, together with the casts which 
I had obtained in New-York, I proposed for these fossils a distinct generic designation; but receiving, soon 
afterwards, Mr. Davidson’s paper “ On the systematic arrangement of recent and fossil 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 Meganteris (Suess), with a reference to Tere¬ 
bratula arcliiaci as the type of the genus. The ligure given in the Pakeontographica so much resembles the 
casts of some of the Rensselasrke, that I inferred the two to be identical, and have thus described these 
fossils in my paper published in the Regents’ Report for 1856 ( Palaeozoic Fossils, 1857); and it was not 
until recently (1858) that my correspondence with Mr. Davidson and Mr. Suess, and the reception of the 
paper of Mr. Suess on the Genus Meganteris, with illustrations, has satisfied me that this genus is quite 
distinct from the Rensseljeria. 
