PALAEONTOLOGY OF NEW-YORK. 
lingula perlata (n. s.). 
Plate IX. Fig. 3-5. 
Shell ovate : beaks subacute : base broadly rounded, having the greatest 
width a little below the centre. Yalves equally convex. 
Surface marked by close concentric lines of growth, the impression of 
which is preserved when the outer shell is removed. Exfoliated surface 
marked by faint concentric ridges, corresponding to those on the 
exterior, and fine scarcely visible longitudinal striae. 
In the specimen fig. 4, the stri£e are generally very closely arranged ; though 
certain portions of the surface present these markings comparatively distant, de¬ 
pendent doubtless on the rate of growth in the shell. 
In the specimen fig. 5, the strife on the upper part of the shell are distant three 
or four times their width, while those on the lower part are close together. These 
variations, and the want of perfect agreement in the surface characters, are scarcely 
of specific value; and without a larger number of specimens, it would be unwise 
to make distinctions. 
Fig. 4. An individual of medium size, preserving the two valves. The outer shell is partially 
exfoliated from the central part of the valve. 
Fig. 3. Profile of the same specimen, showing the convexity of the valves. 
Fig. 5. The lower part of a larger valve having the striae more distant, very thin and 
sharply elevated, while towards the margin they are more closely arranged. 
Fig. 5 a. Enlargement of the concentric lamellae. 
Geological position and locality. In the Pentamerus limestone ( specimen no. 5), 
and in the shaly limestone of the Lower Helderberg group : Albany and Schoharie 
counties. 
Lingula rectilatcra (n. s.). 
Plate IX. Fig. 6 & 8. 
Shell subelliptical : sides parallel, abruptly curving towards the base 
and beak : base abruptly rounded or subtruncate. Cardinal margins 
nearly straight, very convex in the middle and subobtusely carinate 
towards the beak, which sometimes extends a little beyond the body 
of the shell in an acute point. 
