ADDENDA. 413 



Genus Piiolidops (Hall.) 



In 1859, I proposed the name Pholidops for some minute fossils belonging 

 apparently to the family CRANiADiE, but differing from the true Crania in 

 being free or unattached to other bodies, so far as is known. Since that 

 time my attention has been called to the figures of Crania antiquissima of 

 EiCHWALD, as given by de Verneuil, in the Geology of Russia and the Ural 

 Mountains, vol. ii, plate 1, figs. 12, a, b, c. These are cited by McCoy as 

 illustra'tions of typical form of Pseudocrania. In the figure 12 a, we have the 

 characteristic muscular impression of Pholidops; fig. 12 b, can scarcely be- 

 long to the same species since the apex is subcentral. The figures of 

 Pseudocrania divaricata given by McCoy, (British Paleozoic Fossils,) illus- 

 trate a different type; the exterior is represented as radiatingly striate 

 with a distinct area like Trematis, while the interior presents four mus- 

 cular pits as in Crania, and quite unlike the Pholidops of our strata. 

 Prof. McCoy has cited both the above species as typical forms, but in 

 the present state of our knowledge I am not prepared to abandon the 

 Genus Pholidops. 



Pholidops arenaria, (n. s.). 



PLATE III, FIG. 10. See note, page 32. 



Shell rather above the usual size, subcircular, discoid ; beak submarginal 



and slightly elevated ; front margin expanded and flattened. 

 Surface unknown ; interior characterized by a large subcentral muscular 



scar, which in the cast is much deeper on the front margin, and divided 



by a narrow septum. 



This species closely resembles P. oblata of the Schoharie gi-it, but differs in being 

 more nearly circular and in having a much larger area occupied by the muscular 

 impression. The largest specimens measure a little more than one-fourth of an 

 inch in length. 



Geological formation and locality. In the Oriskany sandstone in the town of 

 Knox, Albany county, N. Y. 



[Paleontology IV.] 53 



