PTEROPODA. 191 



Formation and locality. In some compact layers of the upper part of the 

 Chemung group, associated with Bellerophon Mara and Loxonema postremum, near 

 Nichols, Tioga county, N. Y. 



HYOLITHES, Eichwald. 



The genus Hyolitiies was founded by Prof. Eichwald in 1840, who gave the 

 following definition: 



" The bodies which I name Hyolithes are very peculiar ; they appear to be 

 the internal moulds of tubes, but I do not know from what animals they are 

 derived ; it is possible that they belong to genera like Orthoceratites. 



" These bodies are linguiform, terminated in a somewhat flattened point, 

 but still somewhat convex on each of the plain sides, so that they have a 

 thickness of four and a half lines, and a width of six and a half lines. There 

 are others less completely preserved, which are wider and longer" (Sil. Schicht. 

 Sysl. in EMI., p. 97). 



Following this definition, the author describes Hyolithes acutus, in which he 

 observes that the shell is striated in two directions ; and farther notices that 

 the interior of the shell is divided into a series of parallel and oblique divisions 

 or chambers. He places the Hyolithes provisionally among the Cephalopads. 



In the same year (1840), bodies of identical form were described and figured, 

 by Count Mcnster, under the name of Orthoceras anceps (Beitrage, vol. 3, p. 

 104, pi. 9, fig. 6). 



In 1843 Capt. Portlock described a species of this genus from the Lower 

 Silurian rocks of Ireland, under the name of Orthoceras triangulare (Rept., p. 

 375, pi. 28 A, figs. 3 a, b, c), placing the same under the head of doubtful 

 Orthoceratites. 



In 1845 M. E. de Verneuil and Count Keyserling expressed an opinion 

 that the bodies described by Prof. Eichwald were the internal moulds of the 

 siphon of Orthoceratites (Russia and the Oural Mis., vol. 2, p. 350). 



In 1845 "Sowerby founded the genus Theca upon a similar fossil from New 

 South Wales, and this generic term was adopted by Morris, Sharpe, Hall, 

 Salter, Marie Roualt, McCoy, de Verneuil, Barrande, Hawse, F. Rcemer, 

 Schmidt, Prof. Quenstedt, E. Boll, E. Billings, R. Ludwig, Prof. Angelin, 



