332 
PALAEONTOLOGY OF NEW-YORK. 
however, the concentric lines of growth are visible, and in a still less degree the radiating striae. 
The valve fig. 5 a is a young shell, and the radiating striae are very conspicuous, while the 
lines of growth are still visible. The specimen fig. 5 b maintains nearly the same proportions 
as fig. 4, and showing slight indications of radiating striae upon the interior, though in a less 
degree than in fig. 5 a. 
In the young shell the wing is not so distinct as in the older individuals; and in fig. 5 b , 
this part of the shell is represented too large. 
Fig. 4. Cast of the left valve. 
Fig. 5 a. The interior of the left valve of a young shell. 
Fig. 5 b. The interior of the left valve of a full grown individual. 
Position and locality. In the Coralline limestone at Schoharie. 
(Collection of John Gebhabd junior.) 
694. 14. AYICULA LIM^FORMIS (n. sp.). 
Pl. LXXV. Fig. 6 a, b. 
Shell slighly oblique ; height much greater than the width ; anterior wing scarcely defined ; 
posterior wing slightly extended beyond the width of the shell, and strongly wrinkled ; surface 
marked by strong radiating plications, most of which continue undivided to the base; con¬ 
centric lines of growth conspicuous. 
The specimen fig. 6 a is a cast of the interior of the right valve, the posterior wing of which 
is broken off : the plications are quite distinct and angular, being of less width than the spaces 
between. In the specimen fig. 6 b , which is the interior of the right valve, the spaces between 
the plications are nearly flat, and much wider than elevated folds of the exterior surface. In 
this specimen also the posterior wing is imperfect. 
The aspect of fig. 6 a is unlike Avicula ; but in comparison, it should be recollected that 
the wing in entire specimens is much more extended, and the figure should have been drawn 
to show this character. 
Position and locality. In the Coralline limestone at Schoharie. 
(Collection of John Gebhard junior.) 
Several other species of this class of shells have been found in this limestone, but they are 
uniformly in the condition of casts, and often so much distorted by pressure and obscured by 
weathering that they afford no very satisfactory information. 
