26 NEW YORK STATE MUSEUM 



Dalmanella subaequata Conrad, var. pervetus Conrad 



Ortbis perveta Conrad, Acad. nat. sci. Phil. Proc. 

 1843. 1:333 



In the gray crystalline limestone, valves of a Dalmanella were 

 found, which on account of their rather broad form, somewhat 

 ventricose valves with a broad distinct sinus in the pedicle valve, 

 and numerous thin bifurcating striae, have been referred to the 

 group of Dalmanella s u b a e q u a t a. Winchell and 

 Schuchert suggest that only the variety pervetus of Dal- 

 manella subaequata occurs in New York and Canada. 

 In the strong development of their somewhat angular sinus, in 

 the character of the striae, which are a little coarser than the 

 figures of Dalmanella subaequata would indicate, all 

 the writer's specimens agree better with that variety, though 

 they are of slightly larger size than the measurements and figures 

 given by Conrad and Hall require, and in this regard correspond- 

 ing better with the specimens figured by Winchell and Schu- 

 chert. Dr White reports D. subaequata from the Lower 

 and Middle Trenton of the Trenton and Rathbone brook sections 

 in New York. (Group 7) 



parastrophia Hall & Clarke 

 Farastrophia hemiplicata Hall 

 Atrypa hemiplicata Hall. Pal. N. Y. 1847. 1:144 

 Parastrophia hemiplicata was found in the gray 

 crystalline limestone in a few rather gibbous specimens with not 

 very strongly developed folds. This form, whichi has a wide 

 geographic distribution, having been reported by Schuchert from 

 Baffin Land and also from the northwest, is considered to be 

 restricted to the Trenton, but it has been found in the upper 

 Utica beds of the neighborhood of Albany, and is reported by 

 White as marking a zone in the upper Black river beds near 

 Boonville. (Group 7) 



protozyga Hall & Clarke 

 Frotozyga exigua Hall 

 Atrypa exigua Hall. Pal. N. Y. 1847. 1 :141 

 This small form was found to be quite common in the pebbles 

 of gray crystalline and compact reddish gray limestone. While 



