54 



Pj\L^ONTOLOGy OP NEW-YORK. 



434. 13. LINGULA OBLONGA. 



Pl. XX. Fig. 1 a, b, c, d. 



Lingula oblonga. Conrad ; Annual Geol. Report of 1839, p. 65. 



Lingula clintonii. Vanuxem, Geol. Keport Third Dist. N. Y., 1842, p. 79, fig. 4. 



/singula oblonga. Geol. Rep. Fourth District, 1843, p. 77. 



Shell oblong, the sides nearly straight and parallel ; abruptly rounded or sub-acute above ; 

 truncate, with scarcely rounded angles at the base ; flat below, and very convex towards the 

 beak, the shell extending thence in a ridge ; surface marked by concentric lines of growth 

 and fine longitudinal or sub-radiating striae. 



The general aspect of the surface is smooth, but the longitudinal lines are often more dis- 

 tinct than the concentric lines. The shell is very flat at the base, but is elevated into a ridge 

 towards the beak. The general proportions of the shell are somewhat variable, owing, par- 

 tially, to pressure ; but it is readily distinguished by its straight nearly parallel sides, and 

 nearly equal width throughout. 



Fig. 1 a. A young individual of this species. 

 Fig. 1 b. A specimen of the ordinary size of this shell. 

 Fig. 1 c. Specimen longer than the usual form. 



Fig. 1 d. A portion of the surface enlarged, showing the longitudinal striae and concentric lines 

 of growth. 



Position and locality. This species occurs in the sandstone of the lower part of the group, 

 at a quarry near Martville, Cayuga county. {State Collection.) 



435. 14. LINGULA OBLATA. 



Pl. XX. Fig. 2 a, b, c. 

 Lingula ohlata. Hall, Geol. Rep. 4th Dist. N. York, 1843, p. 77 ; fig. 8, p. 76. 



Shell very wide in proportion to its length (length and width usually as 8 to 6 or 9 to 7) ; 

 base truncated ; surface marked by exceedingly fine concentric striae, which appear under a 

 magnifier as if crenulated ; interior of the valve marked by a longitudinal depressed line. 

 Some apparent longitudinal folds or striae in a single specimen. 



This shell differs from the preceding one very essentially, and is readily distinguished by its 

 close fine striae, which are evenly distributed over the surface : in addition to these, there are 

 concentric undulations or folds sometimes very distinctly preserved towards the margin. The 

 interior of the shell is nearly smooth, with the exception of the longitudinal impressed line, 

 and a few partial concentric folds near the beak. 



Fig. 2 a. A figure of an individual of the ordinary size of this species. 



Fig. 2 J. A portion of the surface enlarged. 



Fig. 2 c. The inner surface of a specimen, showing the longitudinal depressed line. 



