4S9 PALAEONTOLOGY OF NEW-YORK, 



£atonia. 



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 singular is\, 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 Eatonia;]:, describing several species. The genus may be cha- 

 racterized as follows : 



Gewijs EatowaII (Hall, 1856). 



Genekic 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 tlie Palajontology of New-Tork, 1841, pa. 56, pi. f. 11. 



t 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 iu Troy, from its estahlisb- 

 ment in 1824, to his death in 1842. 



i Report of the Regents of the Univereity on the State Cabinet of Natural History for 18&6, published 

 1857. Also New Species of Paleozoic Fossils, 1857. 



