Neiu Species of Devonian Fossils. 125 



found in the Rockhouse shale in Tennessee, and the description 

 is based upon specimens from the equivalent faunal horizon in 

 the Arbuckle Mountains of Oklahoma. Collections at Yale made 

 by Doctor C. A. Reeds show that the Rockhouse faunal zone is 

 present in Oklahoma between the Henryhouse and Haragan 

 formations. 



The shell rather closely resembles D. gihhosa, but upon com- 

 parison with the type of Hall's species, it was seen to be a dis- 

 tinct form. The distinguishing features may be summed up as 

 follows: The ventral beak in D. gihhosa is smaller and more 

 neatly pointed than in the new species. Its ventral sinus is more 

 obscure and is confined entirely to the anterior portion of the 

 valve, the central part of the umbonal region being evenly ven- 

 tricose, while in the new species the sinus is more sharply 

 defined and extends as a distinct flattening entirely to the beak, 

 as in D. reticulata. The coarseness of the surface reticulations 

 is also distinctive, six pits in the new species occupying the space 

 of nine in D. gihhosa. 



Occurrence: Rare in the Rockhouse shale at Rockhouse, Har- 

 din County, but common in an equivalent zone in the Arbuckle 

 Mountains of Oklahoma. 



FAMILY STROPHOMENID^ 



Leptaena ingens, n. sp. 



Plate n, fig. 24 



Description: Shell very large, semi-elliptical, and gently con- 

 cavo-convex but not geniculate. Hinge-line straight, making the 

 greatest width of the shell ; lateral margins usually very slightly 

 contracted below the hinge, curving evenly into the regularly 

 rounded anterior margin. Ventral valve varying from slightly 

 to moderately convex ; curvature stronger near the beak and 

 near the anterior margin than over the middle portion of the 

 valve. Muscle-scars strongly impressed, similar to those in L. 

 rhomhoidalis. Surface marked by fine radial striations as in that 

 species, and the posterior portion, only, bearing rather fine and 

 subdued concentric undulations. 



Dimensions: Length, 49 mm. ; width, 60 mm. Convexity vary- 

 ing from 6 to 12 mm. 



