658 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
LEPIDOCYCLUS sp. 1 
Plate 130, G, figures 36, 37 
Views of the interior of the pedicle and brachial valves of Lepidocyclus are 
introduced for comparison with the same views of Rostricellula and Rhyn- 
chotrema. 
Figured specimens.—117209a,b. 
Horizon and locality—Fernvale formation, in Oklahoma: Quarry at Law- 
rence, southwest of Ada, Pontotoc County. 
Family OLIGORHYNCHIIDAE Cooper, new Family 
Small, strongly costate shells with small triangular deltidial plates and strong 
dental lamellae in the pedicle valve ; brachial valve with long crura supported by 
delicate, discrete plates. 
Genus OLIGORHYNCHIA Cooper, 1935 
Oligorhynchia Coorer, Amer. Journ. Sci., vol. 29, p. 49, 1935. 
Shell small, triangular in outline, biconvex; beak nearly straight. Anterior 
commissure intraplicate. External surface costate. Foramen elongate-oval, del- 
tidial plates small, triangular. 
Dental plates of pedicle valve strong, divergent ; teeth long and slender, curved. 
Notothyrial cavity long, moderately deep, narrow; sockets deep; socket ridges 
high; hinge plate divided, supported by thin, delicate convergent plates; crural 
bases triangular; crura long, nearly straight or curved, and extending almost 
directly anteriorly or obliquely toward the pedicle valve. Hinge plate supported 
by inner swelling of posterior of valve which forms the median sulcus at the 
posterior of the brachial valve. Musculature unknown. 
Genotype——Oligorhynchia subplana Cooper, Amer. Journ. Sci., vol. 29, p. 49, 
1935. 
Discussion.—Acquisition of material that could be etched to expose the crural 
plates well is the basis for the revised generic description above. The specimens 
came from the belt of shale and limestones (Hogskin member of the Lincoln- 
shire formation) that extends from Thorn Hill, Tenn., to Washburn, Luttrell, 
and Speers Ferry, the same belt that produced the type specimens. The new 
material presents the hinge plate and shows it to be attached to the inner swell- 
ing of the valve produced by the sulcus at the posterior end and further sup- 
ported by delicate converging plates. This sulcus in a short distance suddenly 
reverses to become a strong median elevation. The hinge plate is divided and 
consists of triangular outer hinge plates and strong, elevated socket plates that 
define the deep socket. The crura are shown by three specimens to have been 
long simple rods extending nearly straight into the valve in an anterior direction. 
A third specimen somewhat deeper than the others and approaching O. subplana 
gibbosa shows the crura to be curved and extended obliquely toward the pedicle 
valve. 
