433 
PALAEONTOLOGY OF NEW-YORK. 
Eatonia. 
In the Annual Report on the Palaeontology of New-York for 1841, Mr. 
Conrad described and figured a species of brachiopod from the Oriskany 
sandstone under the name of Atrypa peculiaris*. A similar species was 
described by Mr. Vanuxem, in his Geological Report in 1843, under the 
name of Atrypa smgularisf, from the Shaly limestone of the Lower Hel- 
derberg group. 
These species are both remarkable in their form and exterior surface 
markings; having one valve deeply sinuate on its anterior margin, and 
the other with a long linguiform extension filling the sinuosity, while the 
surfaces are finely marked by radiating striae. A third species, described 
by Mr. Vanuxem as the Atrypa medialis, was placed in the same group with 
the two preceding, though the external appearance would scarcely justify 
such an arrangement. 
In the course of continued collections in the Helderberg, numerous 
casts of these species were obtained; and it became apparent that they 
possessed a peculiar internal structure, leaving upon the casts similar 
muscular and vascular impressions. For these forms I proposed, in 1856, 
the name EatoniaJ, describing several species. The genus may be cha¬ 
racterized as follows : 
CrENUS EatOjVIAH (Hall, 1856). 
Generic Description. Shell oval or ovoid, subcircular, elongate or trans¬ 
verse. Valves very unequally convex, with a strongly developed mesial 
fold and sinus. Beak perforate. 
* Annual Report on the Palaeontology of New-York, 1841, pa. 56, pi. f. 11. 
f Report on the Third Geological District of New-York, 1843, p. 120, f. 3. 
t In memoriam Professor Amos Eaton, Principal of the Rensselaer School in Troy, from its establish¬ 
ment in 1824, to his death in 1842. 
|| Report of the Regents of the University on the State Cabinet of Natural History for 1856, published 
1857. Also New Species of Palaeozoic Fossils, 1857. 
