190 THE DEVONIAN OF MISSOURI. 



some of these present a median flattening or sinus pretty well defined on the earlier 

 portions of the ventral valves though this disappears in later growth. This median 

 depression is one of the differentials of the smaller species L. tangens and L. adnascens 

 and may indicate the possibility that the latter represent miniature conditions of L. 

 concava. The presence of Leptaenisca concava in these beds is our first knowledge of the 

 occurrence of the genus outside of the early Devonic of New York. The species are 

 rare members of the Helderbergian fauna. At Dalhousie the shells are quite abundant." 1 

 Schuchert figures a ventral valve from Maryland which is depressed medially, and 

 whose hinge line is less than the greatest width of the valve. 2 



Superfamily Pentameracea 

 Family Porambonitidae 

 Genus Anastrophia Hall 



Anastrophia verneuili (Hall) 

 Plate 47, figures 17-21; plate 48, figures 1-9 



Atrypa lacunosa Vanuxem (not Sowerby), 1842, Geol. N. Y., Rept. 3rd Dist., p. 117, 



fig. 3 and p. 119. 

 Pentamerus verneuili Hall, 1857, 10th Ann. Rept. N. Y. State Cab. Nat. Hist., p. 104, 



figs. 1, 2. 

 Pentamerus verneuili Hall, 1859, Pal. N. Y., vol. Ill, p. 260, pi. XLVIII, figs. 1 a-i, 



k-p, r-v, x, y, 1861. 

 Pentamerus verneuili Billings, 1863, Geol. Canada, p. 957, fig. 453. 

 Anastrophia verneuili Miller, 1889, N. Am. Geol., Pal., p. 334. 

 Anastrophia verneuili Hall and Clarke, 1893, Pal. N. Y., vol. VIII, pt. II, pp. 224, 225, 



pi. LXIII, figs. 31-38; pi. LXXXIV, figs. 43, 44, 1894. 

 Anastrophia verneuili Girty, 1899, U. S. Geol. Surv., 19th Ann. Rept., pt. Ill, p. 565. 

 Anastrophia verneuili Dunbar, 1919, Tenn. Geol. Surv., Bull. 21, pi. 2, fig. 14. 



Description — -"Shell subglobose; transverse diameter generally greater than the 

 height. Ventral valve nearly circular or transversely elliptical, more depressed than the 

 opposite, having a distinct sinus, commencing near the beak and regularly widening 

 and deepening to the front, where it terminates in a short truncated extension fitting 

 into a corresponding depression in the front of the other valve; beak shorter than the 

 opposite, perforated by a triangular or subcircular foramen, which is generally covered 

 by the strongly gibbous incurved beak of the other valve. Dorsal valve very much 

 elevated; beak extremely gibbous or ventricose, and strongly incurved. Surface marked 

 by from twenty-four to thirty sharply angular elevated plications, which increase by 

 interstitial addition and bifurcation; from four to six of the plications on the ventral 

 valve usually occupy the sinus; while from five to eight of those on the dorsal valve are 

 very slightly elevated, so as to form a flat rather indistinct mesial fold. 



"[Remarks] * * The larger valve is the dorsal, and bears the two internal 



septa; while the smaller valve, or that with the sinus, is the ventral valve, having the 

 triangular cavity beneath the beak, with a perforation at the extremity, and the dental 

 lamellae are produced into the elongated cavity * * and which, from the 



thickening of the valve, is often affixed to the shell at its base without the intervention 

 of the usual septum, which, when present, is a very subordinate feature. The dental 

 lamellae are lobed on the outside * * leaving a space for the interlocking 



of the septa or brachial lamellae of the opposite valve. The dorsal valve is marked by 

 two converging septa, which extend scarcely more than one-third of the length of the 

 shell, and terminate in a thickened ridge in the deepest part of the valve. From these 



'N. Y. State Mus., Mem. 9, pt. 2, p. 46, 1909. 

 »Md. Geol. Surv., L. Dev., pi LVII, flg. 5, 1913. 



