MARYLAND GEOLOGICAL SURVEY 271 



slightly incurved, and does not rest against the brachial valve. The 

 delthyrium is open throughout life. None of the specimens in the collec- 

 tion show the deltidial plates. 



" Casts of the interior of the brachial valve show a low septum which 

 extends about one-third the length of the shell. This septum divides at 

 its posterior end as in the typical species of Camarotoechia, but there 

 is no cardinal process as in Rhynchotrema." Baymond, 1911. 



One of the most abundant and characteristic Upper Chazyan (Val- 

 cour) fossils of the Lake Champlain region in New York and in Canada. 



Occurrence. CHAMBERSBURG LIMESTONE (Caryocystites bed). In the 

 strip of outcrop from Fort Loudon to Blue Spring, Franklin County, 

 Pennsylvania. 



Collections. Maryland Geological Survey, U. S. National Museum. 



Genus ORTHORHYNGHULA Hall and Clarke 

 ORTHORHYNCHULA LINNEYI (James) 



Plate LVII, Figs. 9-12 



Orthis f linneyi James, 1881, Paleontologist, vol. v, p. 41. 

 Orthorhynchula linneyi Hall and Clarke, 1893, Pal. New York, vol. viii, pt. 2, 

 p. 181, pi. Ivi, figs. 10-13, 19. 



Description, "Shells rhynchonelloid in contour; hinge-line short, 

 straight, extending for about one-third the transverse diameter of the 

 valves. A true cardinal area is present on both valves, that of the pedicle- 

 valve being considerably the broader, erect, often incurved. Each valve 

 also possesses a distinct triangular delthyrium, that of the pedicle-valve, 

 according to the evidence at hand, never being in any degree closed by 

 deltidial plates. External surface strongly and simply plicated, the 

 median fold and sinus being well developed. On the interior, the pedicle- 

 valve possesses blunt teeth which rest upon the laterally thickened walls 

 of the valve and are not supported by lamellae. Between, and slightly 

 in front of these lies a short, subquadrate muscular scar. The brachial 

 valve possesses a linear cardinal process, on either side of which are two 

 discrete crural plates, sharply concave on the upper surface and diverging 



18 



