Maryland Geological Survey 557 



DOUVILLINA ARCUATA (Hall) 



Plate XLIX, Figs. 14-17 

 Strophodonta arcuata Hall, 1858, Geol. of Iowa, p. 492, pi. iii, figs. 1, 2. 



Description. — This little species, first described from the upper De- 

 vonian beds of Lime Creek and Hackberry Grove, Iowa, was identified 

 some years ago in the Chemung beds lying near the base of the formation, 

 in Ontario County, New York, where it is associated with a number of 

 other western species.' Elsewhere in the Chemung of New York the 

 species has not been recorded. 



Douvillina arcuata is of the same tj'pe of generic structure as its asso- 

 ciate D. cayuta and the Hamilton species D. inequistriata Conrad, char- 

 acterized by its subcircular and elevated ventral muscular platform and 

 the divergent fulcra between the anterior and posterior pairs of adductor 

 scars in the dorsal valve. In contour the shell has a flattened umbonal 

 area and a rather abrupt deflection and long slope to the anterior margin. 

 Indeed in these respects the shell is rather more convex than specimens 

 from the Iowa localities. The surface bears quite regularly fasciculated 

 striae. The shell is always small and its dimensions are quite in con- 

 sonance with those of the species as elsewhere found. 



Length 15 mm.; width 17 mm. 



Occurrence. — Jennings ForMxItion, Chemung Member. Garrett 

 County, between Oakland and Deer Park and 2 miles south of Oakland 

 and in Green Glade Eun; near Eedhouse; National Eoad, 6^ miles 

 west of Frostburg. 



Collection. — Maryland Geological Survey. 



Genus STROPHONELLA Hall 



Strophonella cf. reversa (Hall) 

 Plate XLIX, Fig. 18 



strophodonta reversa Hall, 1858, Geology of Iowa, vol. i, pt. ii, p. 494, pi. iii, 



fig. 4. 

 Strophonella reversa Hall and Clarke, 1892, Paleontology of New York, vol. 



viii, pt. i, pi. xii, figs. 16-20. 



■ Clarke, Bull. U. S. Geol. Survey, No. 16, 1885. 



