Maryland Geological Survey 353 



Camarotceciiia litciifieldensis (Schuchert) 

 Plate LXIII, Figs. 11-14 

 Atrijpa sp. Hall, 1852, Nat. Hist. N. Y., Pal., vol. ii, p. 330, pi. Ixxiv, figs. 3 



and 12. 

 Rhynchonella agglom.erata Weller, 1903, Geol. Survey N. J., Pal., vol. iil, pp. 



234-235, pi. xxi, figs. 5-11. 

 Rhynchonella (?) litchfleldensis Schuchert, 1903, Amer. Geol., vol. xxi, p. 167, 

 figs. 



Description. — " Sliell subtriangular, usually a little wider than long, 

 the valves subequally convex, the postero-lateral margins tapering to the 

 beak, where they form an angle of about 90° ; the lateral and anterior 

 margins rounded. Pedicle valve most prominent near the umbo, the beak 

 sharply pointed, arched over that of the opposite valve; mesial sinus 

 rather shallow, rounded in the bottom, not extending back to the center 

 of the valve. Brachial valve most prominent at and in front of the middle ; 

 mesial fold not conspicuous, except near the front margin. Each valve 

 marked by from eighteen to twenty-two simple, angular plications, three 

 of which are usually included in the sinus of the pedicle valve. The finer 

 markings of the shell, if they were present, have been obliterated by ex- 

 foliation. The dimensions of an average adult specimen are: Length 

 !) mm.; width 9.5 mm., and thickness 5.5 mm." Weller, 1903. 



This small shell is very abundant in the Chonctcs jersey ensis zone of the 

 Keyser member. It is distinguished from Rhynchonella transversa of 

 the Helderberg by its smaller size, and by the fact that the fold and sinus 

 are not so broad except in the larger specimens.' It is also more gibbous 

 and less transverse. Camarotachia litciifieldensis also resembles Rhyncho- 

 nella neglecta from the Clinton and Niagara faunas. It differs from R. 

 neglecta in having more plications with the fold and sinus narrower only 

 in the small individuals, the sinus and fold broadening in the larger forms. 

 This form, which has been found in the Cobleskill of New York, has been 

 identified as R. neglecta, so closely does it resemble it. 



Occurrence. — Helderberg Formation, Keyser Member. At all ex- 

 posures of the Chonetes jerseyensis zone. 



Collection. — Maryland Geological Survey. [Maynard.] 



* The individual figured by Schuchert in American Geologist, vol. xxi, p. 167, 

 1903. is much enlarged, although no mention is made of that fact. 

 23 



