352 Systematic Paleontology 



ventral sinus but one. Further, there are from twelve to fifteen plications 

 on a valve against from ten to nineteen in the latter species. 



Length 11 mm.; width 13 mm. 



Occurrence. — Oriskany Formation, Eidgely Member. Ivnobly 

 Mountain near Cumberland. 



Collection. — U. S. National Museum. 



[Rowe.] 



Camarotcechia ( ?) lamellata (Hall) 



Plate LXIII, Figs. 9, 10 



Atrypa lamellata Hall, 1852, Nat. Hist. N. Y., Pal., vol. ii, p. 329, pi. Ixxiv, 



figs, lla-h. 

 Rhynchonella ( ?) lamellata Schuchert, 1897, Bull. U. S. Geol. Survey, No. 87, 



p. 359. 



Description. — " Subrhomboidal, the ventral valve more convex; beaJc 

 of the dorsal valve incurved, small, acute and prominent; surface marked 

 by six or seven plications on each side of the mesial lobe and sinus, which 

 are simple from their origin; mesial sinus marked by two plications, with 

 three corresponding ones on the opposite valve (rarely three plications 

 in the sinus, and four on the corresponding elevation) ; plications crossed 

 by strong imbricating lamellae, Avhich are deeply arched, giving the sur- 

 face a rugose aspect. This species bears a close resemblance to Atnjpa 

 rugosa; but all the specimens examined are nearly uniform in size, and 

 not so large as the larger ones of that species. The plications are also 

 simple from their origin, though marked by imbricating lamellae much in 

 the same manner." Hall, 1852. 



The shell is often subcircular in outline. In nearly all individuals seen 

 in Maryland the mesial elevation is formed by two plications which 

 coalesce towards the beak, one plication is found in the mesial sinus and 

 three to four plications on each side of the sinus and fold. It has been 

 established that no spirals occur in these shells, hence Schuchert removes 

 this species from among the Atrypas. Its generic position is not assured. 

 This species is abundant in the Tonoloway of Maryland. 



Occurrence. — Helderberg Formation, Keyser Member. Pinto, 

 Market Street Bridge and Viaduct Cumberland, Cash Valley. 



Collection. — Maryland Geological Survey. [Maynard.] 



