Maryland Geological Survey 359 



CaMAROTCECHIA (PlETHORHYNCHA) BARR^iXDII (Hall) 



Plate LXIV, Figs. 2, 3 

 Rhynchonclla barrandi Hall, 1857, Tenth Ann. Kept. N. Y. State Cab. Nat. 



Hist, p. 82, figs. 1-3; p. 84, fig. 4. 

 Rhynchonclla barrandi Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 442, pi. 



ciii, figs. 3-8, 1861. 

 Rhynchonella septata Hall, 1859, ibidem, p. 443, pi. ciii, fig. 2, 1861. 

 Plethorhyncha barrandi Hall and Clarke, 1893, ibidem, vol. viii, pt. ii, p. 191. 



Description.— " Shell very large, ovoid or subglobose; full-grown speci- 

 mens higher than wide, vertically flattened on the sides : dorsal valve very 

 convex, often extremely elevated; beak incurved; cardinal border on each 

 side of the beak profoundly sinuate, for the reception of the thick, strongly 

 projecting lamina^ of the opposite valve: ventral valve much the smaller, 

 strongly arcuate longitudinally, having a broad shallow rounded sinus 

 towards the front, abruptly deflected upwards at the lateral margins which 

 are distinctly angular, prolonged in front into a subtriangular vertical pro- 

 jection. Surface marked by forty to forty-six simple (rarely bifurcating) 

 strongly elevated (angular?) plications on each valve." Hall, 1857. 



In Maryland this species is not always readily separated from C. 

 speaiosa unless the specimens are very large, wider, and have a very large 

 but shallow sinus. Mr. Gordon has an internal cast of the ventral valve 

 having a length of 60 mm., which is larger than the usual New York 

 material. 



Bliynchonella septata Hall is based on the dorsal valve of C. harrandii. 

 R. fitchana Hall holds the same relation to C. harrandii that B. ramsa.iji 

 does to C. speciosa. Both are but variations without the incurved margins. 



Occurrence. — Oriskany Formation, Eidgely Member. Knobly 

 Mountain near Cumberland, more common at Hancock, in the glass sand 

 quarries; Warren Point, Pennsylvania. 



Collection. — Maryland Geological Survey. 



CAMARoxaiciiiA (Plethorhyncha) barrandii var. fitciiana (Hall) 

 Plate LXIV, Figs. 4, o 

 Rynchonella fitchana Hall, 1857, Tenth Ann. Rept. N. Y. State Cab. Nat. 



Hist., p. 85. 

 Rynchonella fitchana Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 441, pi. ciii, 

 figs, la, lb, 1861. 



