^rAK'VI.AXl) GkOI.OGICAL SuiiVEY 579 



('A.ArAKordxiiiA oKi'.icri.Mirs (Hall) 

 Plate LIU, Figs. 20, 27 



RhynehoticUa orbirtdaris Hall, IStiU, 13th Rept. N. Y. State Cab. Nat. Hist., 



p. 88. 

 Rhynchonella (Stenochi.irna) 'Jrhicitlaris Hall, 1SG7, Pal. of N. Y., vol. iv, 



p. 353, pi. Iv, figs. 40-4(!. 

 Camarotachia orbicularis Hall and Clarke, 1893, Pal. of N. Y., vol. vlii, 



pt. ii, p. 192, pi. Ivii, Acs. 4(J-4S, .50. 



Description. — ''Shell snborbiciilar, ventricose <ni tlie doisnl valve; 

 width greater than the length. 



"Ventral valve moderately convex, scarcely gibbons on the umbo; 

 beak incurved; outline gently curving on the lateral ami baso-latsral 

 margins, and the center gently depressed in a broad and strongly detined 

 median sinus. 



"Dorsal valve gibbous in tl)e middle, arcuate from beak to base; sides 

 abruptly curving to the ventral valve; median fold beginning above the 

 middle of the length, and l)ecoming more prominent towards the front. 



" Surface marked by abotit twenty-four or mor<> snbangnlar or rounded 

 ribs, those of the central j)ortion being strong and elevated, and those 

 towards the cardinal slope gradually finer and less distinct. There are 

 four or five plications in the mesial sinus, and from four to six on the 

 mesial fold, which are moderately elevated and gently curving to the 

 front. The plications on the sides are more or less abruptly curved to 

 the margins of the shell. The shell when preserved, is marked by fine 

 close concentric striae." Hall, 18(57. 



Length rather small specimen 15 mm.; width 18 mm. 

 .Occurrence. — .Tennixgs FoiniATioN, Chemung ]\1ehj?kk. Trout Run 

 section near Mountain Lake Paik; 2 miles west of Pawpaw, West Vir- 

 ginia, 3312. 



CoUection. — Maryland Geological Survey. 



Camai!()T(Kciiia EXI:^tIA (Hall) 

 Plate LIV, Figs. 1-4 



Atrypa eximia Hall, 1843, Geol. N. Y. 4th Dist., tab. 66, lig. 4. 

 Rhynchonella (Stenochisma) eximia Hall, 1S67, Pal. N. Y., vol. iv, p. 348, 

 pi. Iv, figs. 1-8. 



