238 SYSTEMATIC PALEONTOLOGY 



Family LINGULIDAE 



Genus LINGULA Bruguiere 



LlNGULA RICINIFORMIS Hall 



Plate L, Figs. 6-8 



Lingula riciniformis Hall, 1847, Pal. New York, vol. i, p. 95, pi. xxx, fig. 2. 

 Lingula (Glossina) riciniformis Hall and Clarke, 1892, Pal. New York, 



vol. viii, pt. i, pi. i, fig. 3. 

 Lingula riciniformis Winchell and Schuchert, 1893, Minnesota Geol. Surv. 



pt. iii, p. 343, fig. 24; pi. xxix, fig. 9. 

 Lingula riciniformis Weller, 1903, Geol. Surv. New Jersey, Pal. 3, p. 144. 



pi. ix, fig. 8. 



Description. Shell oval to subelliptical in outline with the two valves 

 equally convex; an average specimen is 8 mm. long and 4 mm. wide. 

 Anterior margin regularly rounded, lateral margins slightly convex, sub- 

 parallel; postero-lateral margins rounded and apex rather blunt. Sur 

 face nearly smooth or marked by very fine concentric lines of growth 

 Fine radiating striae are sometimes visible. 



As pointed out by Winchell and Schuchert in 1893 this shell is of 

 particular interest in showing the three stages of development very 

 clearly. The first shelled condition or " protegulum " is very small ; 

 second comes a sharply defined circular stage, termed the Obolella stage, 

 distinguished furthermore by its lighter color, and third arises the stage 

 in which the shell begins to assume its specific form. Through the 

 addition of shell substance posterior to the protegulum the apex at 

 maturity is no longer marginal as in the Obolella stage, but has become 

 submarginate. 



Occurrence. MARTINSBURG SHALE (Sinutes bed). Chambersburg, 

 Pennsylvania, and Strasburg, Virginia. Trenton limestone of New York, 

 Canada, Minnesota, and New Jersey. 



Collections. Maryland Geological Survey, U. S. National Museum. 



LINGULA NICKLESI n. sp. 



Plate LVII, Figs. 1-U 



Description. The sandstones of Lower Maysville age in the Appa- 

 lachians contain specimens of a Lingula which upon close comparison 

 prove to be identical with a species from the upper part of the Fairview 



