Helderbeeg FoK-^rATiox IX Maryland 19 



Order TELOTREMATA 



Superfamily RHYNCHONELLACEA 

 Family RHYNCHONELLIDAE 



Genus STENOCHISMA Conrad 



StEXOCHISMA FORMOSA (Hall) 



Plate LXII, Figs. 25-29 



Rhynchonella formosa Hall, 1859, lOtli Ann. Rept. N. Y. State Cab. Nat. Hist., 



p. 76, figs. 1-5. 

 Rhynchonella formosa Hall, 1859, Pal. N. Y., vol. iii, p. 236, pi. xxxv, figs. 6a-?/. 



1861. 

 Rhynchotrema forviosum Schuchert, 1897, Bull. U. S. Geol. Survey, No. 87, 



p. 369. 



Description. — "Shell snbtriaiigiilar or transversely oval; lateral mar- 

 gins forming an angle at the beak of about 90° to 110°. Ventral valve 

 somewhat more depressed than the opposite : beak prominent, arched, not 

 strongly incurved. Dorsal valve larger, declining with a gentle curve 

 towards the margins: beak incurved. Surface marked by twenty to 

 twenty-four simple angular plications on each valve, from two to four of 

 which in the middle are coarser and depressed in the ventral valve, having 

 a corresponding number abruptly elevated upon the dorsal valve; con- 

 centrically marked by fine closely arranged striae." Hall, 1859. 



The specimens referred to this species differ but little from those re- 

 ferred to S. deckerensis, the chief distinguishing feature being the more 

 transverse form of the latter species. 



Occurrence. — Helderberg Formation, Keyser Member. Devil's 

 Backbone, Miller's Spring, Viaduct and Market Street Bridge Cumber- 

 land, Cash Valley, li^ miles northeast of Flintstone, Pinto, Flintstone, 

 Maryland ; Hyndman, Pennsylvania. 



Collection. — Maryland Geological Survey. 



Stenochisma deckerensis (Weller) 



Plate LXIII, Figs. 1-1 



Rhynchonella deckerensis Weller, 1903, Geol. Survey, N. J., Pal., vol. iii, p. 

 234, pi. xxi, figs. 1-4. 



