816 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
intercalated. Between these larger costellae fine radial lines extend from the 
beak to the margin. Between the larger costellae the shell is thrown into nar- 
rowly rounded, often chevron-shaped rugae. The rugae may lie obliquely be- 
tween the costellae or they may form an inverted V. 
Inside the pedicle valve the dental plates are of the receding type, short and 
poorly developed. The muscle area is small and nearly confined to the delthyrial 
cavity. Diductor impressions small. Vascula media short. Teeth small and 
sharp. Pseudodeltidium moderately arched, imperforate. Interarea apsacline. 
Brachial interarea anacline; notothyrium partially closed by chilidial plates. 
Cardinalia sowerbyelloid. Brachiophores elongate, slender, supported by callus 
that joins the cardinal process, chilidial plates, and brachiophores into a tentlike 
structure. Internal median septa poorly formed, short but present near the 
middle of the valve. 
Genotype.—Ptychoglyptus virginiensis Willard (by original designation), 
Bull. Mus. Comp. Zool., Harvard Coll., vol. 68, No. 6, p. 283, pl. 2, fig. 12, 1928. 
Discussion.—This genus was described originally as an ornate type of Rafines- 
quina, but examination of the interiors indicates that the affinities are with Sower- 
byella rather than with Refinesquina. Sowerbyelloid features are revealed by the 
ornamentation and the cardinalia. 
Ptychoglyptus as now understood characterizes chiefly forms from the Effna 
formation and its correlates. This genus has been identified in other rocks than 
those laid down in Mohawkian time, but the interiors of the forms referred to 
the genus have not been described. 
PTYCHOGLYPTUS ? KINDLEI Cooper, new species 
Plate 172, B, figures 7-9; plate 172, C, figures 10-12 
Wider than long, hinge forming widest part; sides obliquely sloping toward 
the middle; anterior margin broadly rounded; larger costellae in 2 or 3 genera- 
tions, 6 or 8 on each side of the median line; rugae large, strong. 
Pedicle valve faintly convex in anterior and lateral profile in the posterior 
three-quarters, more or less strongly geniculated toward the brachial valve in 
the anterior quarter; umbo gently and somewhat narrowly swollen; median 
region slightly convex; lateral and anterior slopes steep. Interior unknown. 
Brachial valve nearly flat to gently concave in lateral profile and with the 
anterior quarter turned abruptly in the direction of the brachial valve. Umbo a 
hollow pit, median and flank regions gently concave. 
Measurements in mm.— 
Brachial Hinge 
Length length Midwidth width Thickness 
Holotype "che es occ s 10.4 ? 27 15.2+ ? 
Paratype (66290b).... ? 7.2 12.4 13.7-+ ? 
s (G6200f ie. 7.9 13.8 15.4? -+ ? 
Si (6620081). enert . ? P ? 1.0 
Types.—Holotype: 66290c ; figured paratypes: 66290a,b, 117392a-c, 123254a; 
unfigured paratypes: 66290d-g, 123254b. 
