e 
792 Report or THE State GEoLoGIsT. 
plications, much finer than those adjoining on each side. Shell 
substance rather sparsely punctate. 
Type, Rhynchospira formosa, Hall. Lower Helderberg group. 
Distribution. Devonian— Lower Carboniferous. 
Subgenus Homeeospira, Hall. 1893. 
(Plate 36, figs. 13-19.) 
Shells similar in exterior to Ruynconosrrra. The hinge-plate 
has no posterior extension, but its anterior lobes are greatly 
developed into long, divergent crural bases. They are separated 
to the apex of the beak and between them lies a small linear car- 
dinal process. There is a stout median septum in the brachial 
valve whose height is equal to nearly one-half the depth of the 
valve. The jugum has an acute stem and its lateral branches are 
of the same width from their origin to the point of union. The 
deltidial plates frequently remain distinct and uncoalesced at 
maturity. 
(Type, Homwospira evax, Hall. Niagara group.) 
Ptychospira, Hall. 1893. 
(Plate 36, figs. 20-23.) 
Shells bearing a few sharply angular radial plications which 
are greatly elevated at the margins of the shell. The median 
plication on the brachial valve is usually divided by a fine sulcus, 
there being a corresponding ridge in the sinus of the opposite 
valve. The beak of the pedicle-valve is erect, and truncated 
obliquely by a circular foramen, beneath which lies a flat delta- 
rium, the plates of which are, as in allied genera, more or less 
completely coalesced. The epidermal layer of the shell is finely 
pitted, the punctations apparently not continuing into the layers 
beneath, but producing a superficial ornamentation not unlike 
that occurring in Eicuwatpia. This ornamented layer extends 
even over the surface of the deltidium. 
The inner laminz of the shell are fibrous 
and more sparsely punctated.. There 
is no deltidial tube in the umbonal cav- 
ity of the pedicle-valve. The linge- - 
Fie. 360.—The jugum of Ptycho. Plate appears to be similar to that 
SEA LO en eee: of Ruynonosprra, with no prominent 
posterior extension, but with conspicuous crural bases which 
are curved upward. The whole process is supported by 
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