706 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
Discussion—This species is characterized by its strongly resupinate profile 
and the presence of Ptychoglyptus-like wrinkles in the visceral region. It is 
thus unlike any other species of Palacostrophomena described herein. This 
species may ultimately receive another generic designation, but it is not possible 
from the material at hand. The brachial interior with its fairly strong median 
ridge agrees with Palaeostrophomena although more material may prove this 
species to be a resupinate form of Ptychoglyptus. 
PALAEOSTROPHOMENA SUPERBA Cooper, new species 
Plate 169, C, figures 13-29; plate 184, E, figures 13-18 
Shell small for the genus, strophomenoid in habit, subtrapezoidal to subtri- 
angular in outline. Cardinal extremities acutely angular to auriculate. Lateral 
margins concave just anterior to the cardinal extremities, slightly rounded and 
oblique to the anterolateral region; front margin narrowly rounded. Anterior 
commissure broadly uniplicate. Surface marked by costellae of unequal size. 
Young shells and the posterior part of older ones marked by a few primary cos- 
tellae, 4 or 5 on each side of a prominent median costella. Between the primary 
costellae 2 generations of intermediate size are intercalated, from 12 to 18 oc- 
cupying a space of 5 mm. at the front margin. Space between intermediate and 
primary costellae covered by fine radial costellae. Posterior margin marked by 
oblique wrinkles. 
Pedicle valve gently convex in the posterior region, becoming gradually con- 
cave at about two-thirds the length where the valve is gently geniculated in the 
direction of the pedicle valve. Umbonal region narrow and convex, extended 
forward as a low fold to about the middle. Anterior third gently concave with 
the concavity extending posterolaterally between the lateral margins and the 
folded median part of the valve. Beak forming a blunt point, extending slightly 
beyond the posterior margin. Interarea broad and flat, strongly apsacline. Del- 
thyrium and pseudodeltidium narrow. 
Brachial valve following the curvature of the pedicle with the posterior third 
gently concave and the anterior two-thirds flat to gently convex. Umbo and 
umbonal region moderately deeply concave and forming a sulcus corresponding 
to the fold on the pedicle valve in the posterior third to half. Sulcus lost where 
valve begins to flatten before geniculating. Region about cardinal extremities 
moderately to steeply sloping toward the margins. Lateral and anterior slopes 
moderately steep but the latter not as steep as the lateral slopes. Interarea shorter 
than that of the pedicle valve, flat to slightly convex, hypercline. Chilidium short, 
narrow, strongly arched. 
Interior of pedicle valve with small teeth consisting of two articulating pro- 
cesses: the tooth proper and a process on the inside of the tooth formed by an 
extension of the sides of the deltidium. Delthyrial cavity moderately deep. 
Dental plates, if present, obscured by callus deposit. Cardinal margin greatly ex- 
tended in an anterior direction by deposition of callus under the palintrope and 
flush with the cardinal edge. Low ridges surround posterior sides of the muscle 
