Maryland Geological Survey 299 



Dalmanella perelegaxs (Hall) 

 Plate LIV, Figs. 14--^3 



Orthis perelegans Hall, 1857, Tenth Ann. Rept. N. Y. State Cab. Nat. Hist., 



p. 44, flg. 1. 

 Orthis perelegans Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 171, pi. xiii, 



figs. 4-12, 1861. 



Description. — " Shell transversely oval : valves nearly equally convex. 

 Dorsal valve siibventricose, more or less depressed along the middle from 

 near the beak to the front : beak small, little elevated above the hinge- 

 line. Ventral valve elevated along the middle from the beak towards the 

 front, and sloping laterally : beak small, pointed, incurved, extending be- 

 yond that of the opposite valve. Cardinal margin generally sloping a 

 little from the beaks, and rounding imperceptibly into the lateral margins. 

 Area narrow, nearly half as long as the width of the shell. Foramen broad 

 triangular, extending nearly to the apex of the beak. Surface marked by 

 fine irregular bifurcating longitudinal striie, crossed by concentric lines 

 of growth." Hall, 1859. 



Length 1.7 cm. to 2.5 cm. ; width 1.7 cm. to 3.0 cm. 



In Maryland this well-known and characteristic New Scotland fossil 

 never attains the large size of Xow York examples, but otherwise the 

 specimens are indistinguishable. D. concinna of the Keyser member is a 

 more obese shell, with more pronounced dorsal sinus and ventral median 

 ridge, and the radial striae are finer and equal in size. 



Occurrence. — Helderbekg Formation, Coeymans Member. Devil's 

 Backbone, Corriganville. New Scotland Member. Keyser, West 

 "\'irginia ; Dawson, Corriganville, Maryland. 



Collection. — Maryland Geological Survey. 



Dalmanella eminens (Hall) 

 Plate LIV, Figs. 24-26 



Orthis eminens Hall, 1857, Tenth Ann. Rept. N. Y. State Cab. Nat. Hist., p. 42, 



text figs. 1, 2. 

 Orthis eminens Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 167, pi. xi, figs. 



7-14. 1861. 

 Rhipidomella eminens Hall and Clarke, 1892, ibidem, vol. viii, pt. i, pp. 210, 



225. 

 Rhipidomella eminens Weller, 1903, Geol. Surv. N. J., Pal., vol, iii, p. 304, pi. 



xxxiv, flg. 9. 



