BRACHIOPODA. 189 



or quite equalling the greatest width of the shell, finely crenulated. Area narrow, lineai , 

 vertically striated. Foramen nearly closed, with a narrow prominent callosity along 

 the centre. Surface marked by strong sharp striae, which increase by bifurcation and 

 interstitial addition, becoming rapidly more numerous and finer towards the margins, 

 and are distinctly punctate in the best preserved specimens. 



"[Remarks] * * * * * * * • * 



" * The striae, even in those scarcely exfoliated, are marked by one 



or two rows of elevated pustules, which are punctate at their extremities, and appear 

 to be the bases of small tubular spines. This character, however, is very variable, and 

 in some specimens obscure upon the surface of the shell, while it becomes conspicuous 

 on the exfoliate specimens, and the casts are strongly punctate, while the interior of the 

 shell is distinctly pustulose. ******* 

 ********* —Hall, 1859. 



Genus Leptaenisca Beecher 



Leptaenisca concava (Hall) 



Plate 47, figures 7-16 



Leptaena concava Hall, 1857, 10th Ann. Rept. N. Y. State Cab. Nat. Hist., p. 47. 

 Ltptaena concava Hall, 1859, Pal. N. Y., vol. Ill, p. 197, pi. XVIII, figs. 2 a-f, 1861. 

 Leptaena? {subgenus?) concava Hall, 1883, Rept. State Geol. N. Y. for 1882, pi. XLVI, 



figs. 30, 31. 

 Leptaenisca concava Beecher, 1890, Am. Jour. Sci., 3rd ser., vol. XL, p. 238, pi. 9, figs. 



1-5. 

 Leptaenisca concava Hall and Clarke, 1892, Pal. N. Y., vol. VIII, pt. I, p. 300, pi. XV, 



figs. 30, 31; pi. XVa, figs. 19-21. 

 Leptaenisca concava Clarke, 1909, N. Y. State Mus., Mem. 9, pt. 2, p. 46, pi. 10, figs. 



7-11. 

 Leptaenisca concava Schuchert, 1913, Md. Geol. Surv., L. Dev., p. 310, pi. LVII, figs. 



2-5. 



Description — "Shell concavo-convex, hemispherical. Ventral valve regularly 

 convex; umbonial region prominent; cardinal margin rounding from the beak towards 

 the lateral extremities. Dorsal valve deeply concave. Hinge line less than the greatest 

 width of the shell. Area of ventral valve broad, that of dorsal valve linear. Foramen 

 triangular, nearly closed above by a thick callosity, the lower part occupied by the promi- 

 nent cardinal process of the opposite valve. Surface marked by very fine close radiating 

 striae, each fifth or sixth one a little more prominent than those between ; crossed by fine 

 regular concentric wrinkles, producing a beautiful subcancellate appearance." — Hall, 

 1859. 



Remarks — The relative width of the hinge line is determinable on but three of the 

 eleven specimens observed. These have their greatest width along the hinge line. 

 The ventral valves of the observed specimens are either flattened or depressed, medially, 

 from the cicatrix to the anterior margin. The radiating and concentric costae which 

 ornament the shells are wavy. 



Hall and Clarke figure two ventral valves of L. concava from New York whose 

 greatest width is along the hinge line. 1 



Clarke says: "When Beecher described the genus Leptaenisca there was but one 

 species known, the L. concava of the Helderbergian. We subsequently described as 

 additional species from the same fauna two smaller forms, L. adnascens and L. tangens 

 which then seemed to differ from the larger both in form, surface sculpture and degree 

 of attachment or size of cicatrix. We have before us in the Dalhousie fauna shells which 

 at maturity present the characters of L. concava; their deeply convex and concave shells, 

 with a cicatrix well developed, the form arched but frequently distorted in growth and 



iPal. N. Y., vol. VIII, pt. I, pi. XV, figs. 30, 31, 1892. 



