FOSSILS OF THE SILURIAN AND DEVONIAN ROCKS. 157 



lations prominent, sub-angular, sometimes rounded on the larger part of the 

 <-one ; closely arranged and sharply angular near the apex, gradually increas- 

 ing their distance; becoming less angular with the increase of the size of the 

 skell and obtuse and rounded towards the aperture. On the outer half of 

 th* shell, tht- spaces between the annulations are greater than the annulations 

 themselves. The interspaces, as well as the annulations, are covered in well 

 preserved specimens with fine, even, transverse striae; the number of which 

 differ greatly. In some specimens there is much irregularity in the distance 

 and development of the annulations towards the aperture. The extreme 

 point of the apex is rarely or never preserved in our specimens. 



Our specimens of this species are always silicitied, and maintain their origi- 

 nal cylindrical form ; they never suffered compression. 



The shells of this species attain a length of one inch rarely more, but 

 usually somewhat less. The largest individual before me, and of which the 

 illustration figure 12, plate 31 was made, measures one-half of an inch ; the 

 figure is enlarged to double size. 



Formation and Locality. Found in the rotten hornstone of the Devonian formation, in Clark 

 county, Indiana, on the northern shore of the Ohio river, opposite its falls, and in the cherty layers super- 

 imposed upon the hydraulic limestone at Watson's Station, on the Ohio and Mississippi Railroad 



Genus Styliola Lesueur. 



Etymology : stylos, a pillar. 



Prof. Ludwig gives the following translation of a description of this genus 

 from M. Barrande : Shell small ; transverse section circular ; closed below, 

 and thicker than in the upper part ; conical. Surface without annulations ; 

 smooth, but with fine striae of growth, and sometimes with fine longitudinal 

 striae ; without longitudinal slit, but sometimes with one or two longitudinal 

 grooves, which do not penetrate the shell ; without operculum, and without 

 interior partitions, but having a persistent point sometimes curved backward. 

 The greatest width is at the opening, which is oblique or normal to the axis 

 of shell. 



Styliola fissurella. HALL. 



Tentaculites fissurella. Hall. Geol. Surv 4th Dist. N. Y. 1843. 

 Not. Tentaculites fissurella, Hall. 111. of Dev. Fossils 1876. 

 Styhola fissurella, Hall. Pal. N. Y., Vol. 6, pt. 2, p. 1781885. 



Shell an extremely slender, elongate cone. Apical portion of shell solid. 

 Apex extremely minute, often bulbiform, and very gradually enlarging to the 

 aperture. 



Surface often smooth and without any visible ornamentation, so far as can 



