PTEROPODA. 
191 
Formation and locality. In some compact layers of the upper part of the 
Chemung group, associated with Bellerophon Mccra and Loxonema postremum, near 
Nichols, Tioga county, N. Y. 
HY OLITHES, 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 fines. There 
are other's less completely preserved, which are wider and longer” (Sil. Schicht. 
Syst. in Ehstl., 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 Munster, 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 Yerneuil and Count Iveyserling expressed an opinion 
that the bodies described by Prof. Eichavald were the internal moulds of the 
siphon of Orthoceratites (Russia and the Oural Mts., voi. 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 Yerneuil, Barrande, Hawse, F. Rcemer, 
Schmidt, Prof. Quenstedt, E. Boll, E. Billings, R. Ludwig, Prof. Angelin, 
