PALEONTOLOGY. 441 



RECOGNIZED SPECIES FROM THE MARCELXUS SHALES 



OF OHIO. 



MOELUSCOIDEA. 



BRACHIOPODA. 



Genus EINGULA Brug. 



Lingula Manni. 



Plate VII, figs. 1 and 2. 

 Lingula Manni Hall. ; 16th Rept. State Cab N. Y., p. 24; Pal. N. Y., vol. 4, No. 6, 

 pi. 2. fig. 3. 



Shell of medium size, longitudinally subovate, somewhat more than half as 

 ■wide as long, very obtusely pointed at the upper end, with subparallel lateral 

 margins, and often rather squarely truncate in front, with rounded basal angles. 

 Substance of the shell thin and polished, with irregular concentric lines of growth 

 which do not produce any marked surface character. Interior of the valves some- 

 times characterized by a thin, hair-like, median ridge, which extends to below the 

 middle of the valve, leaving a distinct median depression on the cast where the 

 substance of the shell has been removed. 



The specimens of this species are usually about three-fourths of an 

 inch in length by a little less than half an inch in width. They vary 

 considerable in outline, the variation being principally in the form of the 

 front, some of them being much more round on the front margin than 

 others, or than the type specimens. This variation also causes a differ- 

 ence in the form of the lateral margins producing a more rounded or 

 oval form, and giving the shells an appearance approaching that of L. 

 Delia Hall, Pal. N. Y., vol. iv, p. 12, pi. 2, fig. 9. The two forms are 

 associated in the shales and can scarcely be considered as distinct species. 

 Many of the specimens are so distinctly like L Manni, that it seems im- 

 possible the others having so slight a difference in form could be dis- 

 tinct, that I have not thought it advisable to attempt their separation. 



Lingula ligeaf 



Plate VII, figs. 3 and 4. 



? Lingula ligea Hall ; Pal. N. Y., vol. 4, part 1, p. 7, pi. 1, fig. 2. 



Shell elongate elliptical in general outline, being about twice as long as wide, 

 rounded on the anterior end, and slightly more pointed at the beak in full grown 

 forms ; but in young or partly grown shells the extremities appear nearly equal. 

 Valve'moderately convex, and sometimes a very little flattened along the middle. 

 Surface marked by fine concentric lines of growth. 



The examples referred with some slight doubt to this species are 

 quite numerous in the thin bedded layers of bituminous limestones from 



