404 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 127 
bifurcated costae. In these respects it resembles D. atavoides but differs in its 
more slender lateral profile, details of the ornamentation, and a differently pro- 
portioned pedicle valve which has much less depth than that of D. atavoides. 
Genus VALCOUREA Raymond, 1911 
Valcourea Raymonp, Ann. Carnegie Mus., vol. 7, p. 239, pl. 35, figs. 15-19, pl. 36, fig. 1, 
text fig. 12, 1911; Valcourea (part) ScHUCHERT and Cooper, Mem. Peabody Mus. Nat. 
Hist., vol. 4, pt. I, p. 97, 1932. 
The specimens described herein permit a reevaluation of the genus Valcourea. 
The description of the genus offered by Schuchert and Cooper in 1932 includes 
two groups of shells now separated under the names Campylorthis and Chaulisto- 
mella. These two genera hitherto included in Valcourea generally occur in later 
strata than those containing Valcourea, and as far as known the three do not 
occur together. 
As repeatedly pointed out, Valcowrea is a member of the Dinorthidae, retain- 
ing many primitive characters, and is probably the earliest known member of 
the family. External as well as internal features distinguish Valcourea from other 
members of the family. A pseudodeltidium and chilidial plates are constant 
features in all known species. Another feature constant in all species described 
herein is the more or less prominent, narrow, carinate fold that originates on 
the umbo of the pedicle valve and extends for a greater or less distance toward 
the anterior margin. This fold is most pronounced in the earliest members such 
as V. intracarinata and V. strophomenoides but is not very marked in an unde- 
scribed species (Valcourea sp. 2) from the Lincolnshire limestone of Tennessee. 
Corresponding to the fold of the pedicle valve is a more or less deep and long 
sulcus extending from the umbo of the brachial valve to the middle or beyond. 
When this sulcus is deep, it helps to emphasize and heighten the median ridge 
inside the brachial valve. 
Inside the pedicle valve perhaps the most characteristic generic feature is the 
more or less strongly developed subperipheral rim which is a common feature of 
convexi-concave shells. This rim may be strongly thickened or may be only poorly 
developed. A negative feature of the genus is the lack of preservation of the 
pallial marks. The course of these sinuses is usually well marked in many mem- 
bers of the Dinorthidae, but only a few specimens of Valcourea have been seen 
that show any details of them. Such a specimen is Valcourea sp. 2 (110257) 
which shows the strong trunks of the vascula media originating at the anterior 
ends of the diductor impressions. These bifurcate almost exactly at their point 
of origin, the inner branches extending anteromedially and the outer ones extend- 
ing slightly anterolaterally. Both sets of trunks are directed chiefly in an anterior 
direction unlike other members of the Dinorthidae in which the bifurcated 
branches extend anteromedianly and posterolaterally. 
In the brachial valve the feature of generic importance is the cardinal process. 
This has a short and stout shaft but a prominent myophore. Generally the 
myophore is trilobed, the amount of lobation depending on the age of the speci- 
