LOWER HELDERBERG GROUP. 
157 
Subface marked by closely arranged subequal concentric striae, and, when 
exfoliated, by fine longitudinal striae, which are likewise conspicuous 
upon the inner side of the shell. Substance of the shell closely lamellose. 
This species is distinguished by its straight parallel sides and abruptly rounded 
base, with sloping cardinal margins, prominent beak, and extremely convex upper 
central portions of the shell. The striae are not conspicuously different from those 
of some other species of Lingula. 
Fig. 6. An individual of medium size. 
Fig. 8. A large individual of the same species. 
Geological position and locality. In the shaly limestone of the Lower Helderberg 
group : Helderberg, Schoharie, Hudson, etc. 
Lingula spatliata (n. s.). 
Plate IX. Fig. 9, 7 & 11. 
Shell oval-ovate, with the sides scarcely curved and gradually converging 
towards the cardinal extremity, which is obtuse : base abruptly 
rounded or sub truncate. 
Sukface marked by concentric lines of growth : vascular impressions 
strongly marked upon the cast. 
This shell differs somewhat in form from L. centrilineata; and the aspect of the 
shell, the interior markings, etc. present well-marked differences : the sides are 
more nearly parallel, and the base less curved and more abruptly sloping towards 
the beaks. 
The specimen represented in figs. 7 and 11 presents many characters in common 
with fig. 9, but it has a broader depression down the centre of both valves, which 
are likewise more convex, and the longitudinal striae are more distinctly diverging 
or radiating than in that one. In the imperfect condition of the specimens, it seems 
more judicious to consider these as varieties of one species, than as distinct species. 
Fig. 9. A large individual having the upper part of the shell broken off. 
Fig. 7 & 11. Two views of a specimen having the base broken off. The convexity of the 
two valves is more than one-third the greatest width of the shell. 
Geological position and locality. In the shaly limestone of the Lower Helderberg 
group : Helderberg mountains and Schoharie. 
