7490 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
ISOPHRAGMA sp. 1 
Plate 213, B, figure 21 
A small brachial valve, nearly plane in profile and with moderately strong 
costellae, was taken in the residues from the Pratt Ferry limestone. The interior 
shows the subparallel plates which in this specimen are somewhat thinner than in 
other species. The discovery is interesting because Isophragma occurs below the 
Pratt Ferry limestone in the upper part of the so-called Lenoir and also in the 
contemporary Little Oak formation. This helps to emphasize the close relation- 
ships of these various formations. 
Figured specimen.—123286. 
Horizon and locality Pratt Ferry formation in Alabama: 0.2 mile southeast 
of Pratt Ferry, Blocton (15’) Quadrangle. 
Family TAPHRODONTIDAE Cooper, new family 
Plectambonitacea having an exterior like Sowerbyella but the brachial valve 
having orthoid cardinalia, thick notothyrial platform, high, bladelike cardinal 
process, and long slender brachiophores. Median ridge formed of 2 subparallel 
plates. 
TAPHRODONTA Cooper, new genus 
(Greek taphros, ditch; odont, tooth) 
Shell small, about 4 inch in width; suggesting Sowerbyites or Sowerbyella in 
appearance; pedicle valve gently convex; brachial valve concave ; anterior com- 
missure rectimarginate; surface multicostellate ; pseudopunctate. 
Pedicle valve with narrowly convex, fairly strongly elevated pseudodeltidium ; 
delthyrial cavity moderately deep; dental plates short and stout; teeth flat, ob- 
lique, double, the two processes separated by a deep, slitlike fossette ; muscle field 
somewhat heart-shaped, the diductor scars wide and oval, the adjustor scars not 
differentiated ; adductor scars small, located between diductors near center of 
muscle field. Median area just anterior to muscle field thickened ; area anterior 
to this median thickening forming a sulcus that extends to the anterior margin; 
lateral areas bounding sulcus thickened and roughened, the thickening not reach- 
ing the margins. 
Brachial interior with thickened notothyrial platform filling or nearly filling the 
notothyrium ; cardinal process a slender median ridge on the notothyrial plat- 
form ; sockets deep; brachiophores long, bladelike, pointed distally but thickened 
by an articulating boss opposite the point where the brachiophore joins the noto- 
thyrial platform; median ridge anterior to notothyrial platform composed of 2 
thick, united septa rising to a crest near the anterior margin; inner margin an- 
terior to median septa thickened and extending as a thick, pustulose band cor- 
responding to the marginal troughlike band of the pedicle valve. 
Genotype.—Taphrodonta parallela Cooper, new species. 
Discussion—The exterior features of this genus form an almost exact con- 
vergence toward other genera in other geological periods. The most distinctive 
