BRACHIOPODA. 197 



wherein the plate is primitively flat but in later forms always has a depressed cardinal 

 pit. As in most lower Devonian terebratulids, the hinge plate is transversed by a well 

 defined visceral foramen, which, beginning dorsal of the anterior edge of the plate, 

 emerges on its surface just below the beak. The adductor muscle scars are narrow, 

 separate and distinctly impressed. ****** 



***** *** ** 



"Shell with the characters of the genus; length of a mature individual 24 mm., 

 width 14 mm., thickness 11 mm. Six to eight plications on the middle of the ventral 

 valve and one more on the dorsal. About three of these plications in a width of 5 mm., 

 on the anterior margin. Hinge plate extremely variable, being in some specimens 

 excavate, in others raised into a median process." — Dunbar, 1917. 



Remarks — A single specimen has been observed. 



Rensselaerina medioplicata var. latior Dunbar? 

 Plate 53, figures 21-24; plate 54, figures 1-4 



Rensselaerina medioplicata var. latior Dunbar, 1917, Am. Jour. Sci., vol. XLIII, p. 469, 



pi. II, figs. 10, 11. 



Description — " * * a shell like R. medioplicata but proportionally much 

 broader and shorter, and with the plications finer and somewhat more restricted to the 

 anterior part of the shell. The length of a fully grown specimen is 20 mm., breadth 

 16 mm., thickness 11 mm. There are four plications in about the width of three in 

 R. medioplicata." — Dunbar, 1917. 



Remarks — The specimens — more or less of the anterior portion of the shell is 

 missing — show no trace of plications. 



Superfamily Spiriferacea 



Family Atrypidae 



Genus Atrypina Hall and Clarke 



Atrypina imbricata (Hall) 



Plate 50, figures 27-29 



Leptocoeha imbricata Hall, 1857, 10th Ann. Rept. N. Y. State Cab. Nat. Hist., p. 108. 

 Leptocoeha imbricata Hall, 1859, Pal. N. Y., vol. Ill, p. 246, pi. XXXVIII, figs. 8-13, 



1861. 

 Leptocoeha imbricata Billings, 1863, Geol. Canada, p. 957, fig. 452. 

 Trematospira imbricata Hall, 1863, Trans. Albany Inst., vol. IV, p. 146. 

 Trematospira imbricata Hall, 1863, 16th Ann. Rept. N. Y. State Cab. Nat. Hist., p. 60. 

 Trematospira ? imbricata Meek and Worthen, 1868, 111. Geol. Surv., vol. Ill, p. 381, 



pi. 7, figs. 2 a-e. 

 Atrypina imbricata Hall and Clarke, 1893, Pal. N. Y., vol. VIII, pt. II, p. 162, pi. 



L1II, figs. 5, 6, 8-10, 1894. 

 Trematospira imbricata ? Keyes, 1894, Mo. Geol. Surv., vol. V, p. 96. 

 Atrypina imbricata Weller, 1903, Pal. N. J , vol. Ill, p. 312, pi. XXXVII, figs. 17-22. 

 Atrypina imbricata Shimer, 1905, N. Y. State Mus., bull. 80, p. 246. 

 Atrypina imbricata Clarke, 1908, N. Y. State Mus., Mem. 9, pt. 1, p. 109. 

 Atrypina imbricata Schuchert, 1913, Md. Geol. Surv., L. Dev., p. 394, pi. LXV11I, 



figs. 4-6. 

 Atrypina imbricata Dunbar, 1919, Tenn. Geol. Surv., Bull. 21, pi. 2, fig. 2. 



Description — "Shell longitudinally semi-elliptical or suborbicular. Ventral valve 

 convex, most prominent along the middle, and sloping laterally; beak small, incurved 

 at the apex and perforated by a very small round aperture, one side of which is formed 



