330 



PALEONTOLOGY OF NEW-YORK. 



689. 60. ATRYPA sp. 



Pl. LXXIV. Fig. 12 a, b, c. 



Rhomboidal ; surface of ventral valve marked by about 19 angular plications, three of which 

 are very slightly elevated in front ; scarcely visible concentric striee, which are waved on the 

 plications. 



This species occurs with the preceding, scarcely differing in form. In a single specimen the 

 plications are more numerous, less raised on the mesial elevation, and almost destitute of con- 

 centric strige, features which eminently characterize the other species. 



Fig. 12 a, A fragment of stone, on which are grouped several specimens of the preceding species, 



with a single one of this species in the centre. 

 Fig. 12 h. Another view of the same. 

 Fig. 12 c. Profile of the elevation of the scrise. 



Position and locality. In the Coralline limestone at Schoharie. 



{Collection of John Gebhard junior.) 



ACEPHALA OF THE CORALLINE LIMESTONE. 



The following have not been seen in any other rock; and though differing from those of the 

 Niagara group in the western part of the State, they are likewise equally distinct from those of 

 the Lower Helderberg limestones which succeed this rock. 



690. 10. TELLINOMYA-? EQUILATERA. 



Pl. LXXV. Fig. 1 a-d. 



Cast of shell nearly equilateral, oval ; anterior extremity more rounded than the posteriorj 

 ■which is sometimes slightly alate ; a distinct groove extends from the inside of the beaks 

 obliquely backwards nearly to the posterior extremity, above and behind which the cast is 

 more compressed ; surface showing faint marks of concentric stria3. 



This species is the most common acephalous bivalve in this rock. It is always found in the 

 condition of casts, which, v.'hen well preserved, show the impression of concentric striae, and 

 a distinct, rather deep, groove extending from the beak nearly to the posterior extremity. In 

 less perfect specimens, the nearly equal extremities and oval form are usually sufficient to 

 characterize the species. 



Fig. 1 a, h. Similar views of two specimens, showing a slight difference in form, probably due 



to pressure. 

 Fig. 1 c. Cardinal view of fig. 1 a. 

 Fig. 1 d. View of the posterior slope, showing the groove in each valve. 



Position and locality. In the Coralline limestone of Schoharie. 



(Collection of Jouk Gebhard junior.) 



