BRACHIOPODA. 187 



deeply grooved for the passage of a pedicle. Surface marked by regular, rounded, radi- 

 ating striae, which increase by bifurcation and interstitial addition; the upper part of 

 the valves marked by strong concentric wrinkles which do not extend below the abrupt 

 bending of the valves. 



"The interior of the shell is striato-punctate, or sometimes simply punctate. The 

 muscular areas of the ventral valve are strong, more or less deeply bilobed, and limited 

 by the extension of the dental lamellae. The interior of the dorsal valve is strongly 

 marked by the muscular impressions; the dental process perforate near its outer surface, 

 or deeply grooved; and there is often a deep cavity below this, extending towards the 

 beak. 



" [Remarks] — This shell exhibits much variety of form, .being sometimes nearly flat 

 or but slightly curved near the margin; and the corrugations are variable in number 

 and strength. In very old shells they are often not as prominent as in younger ones, or 

 those of medium size. The area, as usually exposed, is subject to much variation, and 

 not unfrequently the valves are so closed as to leave no visible area. The beak of the 

 dorsal valve, either at or just within its extremity, shows a rounded perforation or groove ; 

 and the beak of the opposite valve is marked by a rounded, shallow groove, which, 

 extending downwards, often ends in a perforation both in young and old shells. Some-, 

 times the groove only is visible, the perforation having doubtless once existed, but sub- 

 sequently closed. In some specimens there is a simple indentation on the beak" — Hall 

 1859. 



Genus Stropheodonta Hall 



Stropheodonta arata (Hall) 

 Plate 46, figures 33-35 



Strophodonta varistriata var. arata Hall, 1859, Pal. N. Y., vol. Ill, p. 183, pi. XVIII, 



figs, la-i, 1861. 

 Strophodonta varistriata var. arata Hall, 1883, Rept. State Geol. N. Y. for 1882, pi. 



XLIV, figs. 17, 18. 

 Stropheodonta varistriata var. arata Hall and Clarke, 1892, Pal. N. Y., vol. VIII, pt. I, 



pi. XIII, figs. 17, 18. 

 Stropheodonta varistriata var. arata Weller, 1903, Pal. N. J., vol. Ill, p. 275, pi. XXVII, 



fig. 3. 

 Stropheodonta varistriata var. arata Shimer, 1905, N. Y. State Mus., Bull. 80, p. 241. 

 Stropheodonta arata Schuchert, 1913, Md. Geol. Surv., L. Dev., p. 311, pi. LVII, figs. 



7-10. 



Description — "Shell semi-elliptical, with the cardinal extremities more or less 

 salient; hinge crenulate. Dorsal valve more or less concave. Ventral valve varying 

 from moderately convex to very gibbous, and sometimes geniculate towards the front. 

 Area narrow. Foramen none, or a narrow elevation or callosity in place of it. Surface 

 marked by very prominent sharp angular ridges and intermediate fine undulating striae, 

 which cover also the slopes of the ridges. Sometimes a few short wrinkles mark the 

 spaces between the ridges, along the cardinal margin towards the hinge extremities." — 

 Hall, 1859. 



Stropheodonta (Leptostrophia) planulala (Hall) 



Plate 46, figures 36-38; plate 47, figures 1, 2 



Strophodonta planulata Hall, 1859, Pal. N. Y., vol. Ill, p. 184, pi. XVI, figs. 9-12, 1861. 

 Stropheodonta planulata Schuchert, 1897, U. S. Geol. Surv., Bull. 87, p. 426. 

 Stropheodonta planulata Weller, 1903, Pal. N. J., vol. Ill, p. 276, pi. XXVII, figs. 1, 2. 

 Stropheodonta {Leptostrophia) planulata Schuchert, 1913, Md. Geol. Surv., L. Dev., p. 

 315, pi. LVII, figs. 14-16. 



