62 * [Senate 



moderate, narrow triangular. Surface marked by faint concentric 

 lines of growth. 



This species resembles somewhat S. ventricosa of the Lower Helderberg 

 shaly limestone, but has a much higher area. It still more resembles S. 

 lineatus of the Carboniferous system, but differs in its surface markings 

 and its narrower foramen. 



Geological position and locality. Limestones of the Lower Helderberg 

 group, Cumberland ( Md.). 



Spirifer octocostata ( n. s.). 



Pol. N.Y. Vol. ill, pi. 28, f.2. 



Shell subglobose ; valves nearly equally convex : ventral valve 

 most elevated near the beak ; sinus extending nearly to the 

 apex ; beak slightly incurved ; dorsal valve most convex in the 

 middle ; mesial elevation not prominent ; beak rising little 

 above the hinge-line, slightly incurved ; hinge-line less than the 

 width of the shell, rounded at the extremities ; area triangular, 

 faintly defined, somewhat arcuate ; foramen very narrow. Sur- 

 face having about four rounded, slightly prominent folds on each 

 side of the mesial sinus and elevation ; concentrically marked 

 by fine, regular, closely arranged striae. 



This species resembles S. crispus of the Niagara group, but is more 

 globose in form, has a much shorter area, more rounded extremities, and 

 less strongly marked plications. It appears to be intermediate between that 

 species and S. hicostatus of the same group, but may be readily distin- 

 guished from cither. 



Geological iiosition and locality. Limestones of the Lower Helderberg 

 group, Cumberland ( Md.). 



Spirifer submucronatus ( n. s.). 



Pal. N.Y. Yol.iii, pi. 100, f. 3. 



Shell semicircular, with the extremities mucronate; valves equal- 

 ly and moderately convex : ventral valve regularly convex at 



