182 PALEONTOLOGY OF NEW YORK. 



condition that no satisfactory illustration can be given. The Tentaculites 

 gracilistriatus occurs in constant association with the S. fissurclla, and is abundant 

 in the Marcellus shale and lower beds of the Hamilton group, while in the 

 abundant development of the latter fossil in the Genesee slate, the former is 

 comparatively rare. 



Formation and locality. In some compact layers of the Genesee slate to the 

 south of Alden, in Erie county, N. Y. 



Styliola obtusa, n. sp. 



PLATE XXXI A, FIGS. 3t-36. 



Form a minute elongate cone, comparatively robust in its proportions. Apex 

 solid, often obtuse or rounded, and appearing as if worn. 



Surface smooth. Length of ordinary specimens one and a half to two milli- 

 metres, often two and a half, and rarely three millimetres. 



The angle subtended by the sides is greater than in Tentaculites gracilistriatus, 

 and much greater than that of Styliola Jissurella in similar conditions. The 

 surface appears to be entirely smooth, but perhaps it may have been very 

 finely striated in its living condition. The form is round though often 

 appearing, as the result of compression, obtusely subangular towards tha 

 aperture. 



It is distinguished from Tentaculites gracilistriatus by its more obtuse form, 

 especially at the apex, and the absence of annulations. From Styliola fissurella 

 it differs in its stouter and more obtuse form. The apical portion of T gracili- 

 striatus, occurring in the same rock, is distinguished by its more slender form 

 and the obscure annulations in receding from the apex. 



The prevailing form occurring in the shales of the Hamilton group, preserves 

 no visible striae, and the apex is quite obtuse, often appearing as if worn. In 

 some calcareous bands there occur a few specimens of a very similar fossil, 

 which show minute stria), but their identity has not been determined. 



Formation and localities. In shales of the Hamilton group at Darien Centre, 

 Genesee county, and on the shores of Canandaigua lake in Ontario county, N. Y. 



