286 SYSTEMATIC PALEONTOLOGY 



Family LYRODESMIDAE 



Genus LYRODESMA Conrad 



LYEODESMA CONEADI Ulrich 



Plate LIV, Fig. 30 



Lyrodesma conradi Ulrich, 1893, Geol. Surv. Ohio, vol. vii, p. 684, pi. xlvii, 

 fig. 9. 



Description. " Shell a little oblique, transversely subovate, somewhat 

 the highest across the middle of the posterior end; length 15 to 22 mm., 

 height 11.5 to 15 mm., thickness about half the height; just beneath the 

 middle of the slightly oblique posterior margin, the outline is a little 

 produced and more narrowly rounded than elsewhere. Valves moderately 

 convex, the posterior umbonal ridge rounded, not a prominent feature, 

 the beaks small, situated just within the anterior third of the length. 

 Surface marked by very fine, closely arranged, sharp concentric lines, 

 crossed on the posterior cardinal slope by about ten radiating striae. 

 Hinge with seven teeth of the usual type in each valve. Adductor scars 

 distinct, the posterior one rather small and situated a very short distance 

 beneath the submarginal pedal muscle impression. Pallial line with a 

 small though undeniable posterior sinus. A peculiar feature of internal 

 casts is the broad and shallow furrow shown in the figure just in front 

 of the umbonal ridge." Ulrich, 1893. 



Occurrence. MAETINSBUBG SHALE (Eden division). Jordans Knob, 

 one and one-half miles northeast of Fort Loudon, Pennsylvania. Ederi 

 shale at Cincinnati, Ohio. 



Collection. IT. S. National Museum. 



Family MODIOLOPSIDAE 



Genus MODIOLOPSIS Hall 

 MODIOLOPSIS MODIOLAEIS (Conrad) 



Plate LVIII, Fig. 12 



Pterinea modiolaris Conrad, 1838, 2d Ann. Kept. Geol. Surv. New York, 



p. 118. 

 Modiolopsis modiolaris Hall, 1847, Pal. New York, vol. i, p. 294, pi. 81, 



figs, la-g; pi. Ixxxii, fig. 1. 

 Modiolopsis modiolaris Foerste, 1914, Bull. Sci. Lab. Denison Univ., vol. xvii, 



p. 281, pi. iii, fig. 1; pi. v, figs. 1, 2. 



