The !^ew Species of Beachiopoda. 361 



in 'the umbonal region, broadly convex anteriorly and slightly 

 extended on the anterior margin, but with no median sinus. 

 Brachial valve with the median elevation somewhat more strongly 

 defined, especially in the umbonal region. Umbo-lateral slopes 

 rather more abrupt than in the other valve. 



Internal structure normal for the genus. 



Oriskany sandstone. Cayuga^ Ontario. 



Merista Tennesseensis. 



Plate 8, figs. 20-25. 



Merista Tennesseensis, Hall. Palaeontology of N. Y., vol. VIII, pt. 2, p. 365, 

 pi. xlii, figs. 1-6. 1894. 



Shell subpentahedral in outline, transverse, rarely elongate. 

 Yalves subequally convex, with broad, low fold and sinus devel- 

 oped on the anterior portion of the brachial and pedicle-valves 

 respectively. Umbo of pedicle-valve not conspicuous, apex 

 truncated at maturity by a circular foramen. Deltidial plates 

 concealed by incurvature. Umbo of brachial valve full, apex 

 acute. -External surface smooth. Dimensions of an average 

 example: length, IT mm.; greatest width, 19 mm. 



Upper Silurian. Perry county, Tennessee. 



Clintonella vagabunda. 



Plate 9, figs. 17-26. 



Clintonella vagabunda, Hall. Palaeontology of N. Y . , vol . VIII, pt. 2, p, 160, 

 pi. lii, figs. 1-11. 1894. 



Shells small, suboval in outline, valves subequally biconvex, 

 the axis of greatest convexity being oblique. Pedicle-valve with 

 a small umbo, which is compressed laterally, the apex being 

 slightly incurved. Delthyrium wide, without traces of deltaria. 

 The umbo merges anteriorly into a sinus which makes a deep 

 flexure at the margin and bears two plications, both of which 

 reach the beak. The lateral slopes bear from four to eight radial 

 plications of smaller size. On the interior the teeth are promi- 

 nent and strongly recurved. The muscular impression is moder- 

 ately large, flabellate in outline and deeply impressed. The 

 brachial valve has an inconspicuous beak ; the umbonal region is 

 depressed for about one-third the length of the valve, but an- 

 46 



