LOWER HELDERBERG ROCKS. 
265 
Anatina ? sinnata (n. $.), 
Plate XLIX. Fig. 3 a - d, 
Shell tliin, equivalve, compressed, inequilateral, subrhomboid, with the 
posterior side much wider than the anterior ; posterior? rounded, much 
compressed near the extremity, with a distinct shallow groove ex¬ 
tending from near the beak obliquely to the postero-basal margin, and 
a second broad groove extending from the hinge-line, immediately 
behind the beak, vertically to the base of the shell, each one producing 
a slight sinuosity in the margin of the shell : umbones vertical, or not 
perceptibly inclined to either side of the shell; anterior cardinal slope 
nearly flat, compressed and subalate. 
Surface concentrically marked with fine subimbricating striae, which are 
undulated in passing over the depressed lines on the anterior side of 
of the shell. 
This fossil, from the characters preserved, is similar to some forms of Anatina; 
but from the imperfection of the specimens examined, its true relations cannot be 
satisfactorily determined, and I can only refer it provisionally to this genus till we 
shall obtain a better knowledge of its characters. It possesses external characters 
extremely different from any other fossil which has come under my observation. 
Fig. 3 a. The right valve? of a specimen in which the two extremities are imperfect. 
Fig. 8 b. Cardinal view of the same. ( The compression of the anterior extremity is not 
distinctly represented.) 
Fig. 3 c. The right valve? of a specimen from which the shell is nearly exfoliated, and the 
beaks broken off. 
Fig. 3 d. Profile view of the same. 
Geological position and locality. At the base of the Lower Helderberg group, 
Winfield, Herkimer county. 
[ Palaeontology III.] 
34 
