THE KIMMSWICK AND PLATTIN LIMESTONES 
205 
21. The median part of the pedicel valve, for a width of 4 
radiating plications, is distinctly elevated above the rest of the 
valve. Contrasted with the brachial valve, the pedicel valve 
is considerably more convex. 
Found at the top of the Plattin limestone, at Buford Cave, and 
at the Yeager locality, in Balls County. 
The specimens here described agree fairly well with those fig- 
ured by Hall (plate XXII, figs. 5 A, B of this bulletin), from the 
middle Trenton at Martinsburg, New York, as Atrypa (= Zygo- 
spira) deflecta. Zygospira recurvirostris (Hall), from the same 
locality and horizon, differs from Zygospira deflecta chiefly in 
the greater convexity of the brachial valve and in the much 
less conspicuous depression of the median part of this valve. 
If it be possible to separate Zygospira recurvirostris from Zygo- 
spira deflecta by means of these characteristics, then the Plattin 
limestone specimens come nearer to Zygospira deflecta. If these 
two species prove not distinct, then both must bear the name 
Zygospira deflecta, since the original description of Zygospira de- 
flecta precedes that of Zygospira recurvirostris in the original de- 
scription of these species (Paleontology of New York, 1, 1847, 
p. 140, pi. 33, figs. 4 a, b). 
16. Ctenodonta of gibberula group. 
Plate XXI, flg. 13 
A single left valve of some species of Ctenodonta was found 
near the top of the Plattin limestone, about 1 mile northwest of 
Spalding Springs, near the home of H. W. Ogle. Compared 
with Ctenodonta gibberula Salter (plate II, fig. 13 of this bulletin), 
the shell is of smaller height, the ventral margin is much less 
convex, the angle between the hinge areas anterior and posterior 
to the beak is more divergent, and the entire aspect of the shell 
is more elongate. 
