BRACHIOPODA. 365 



Meristella Walcotti, sp. nov. 



PLATES XLUI, FIGS. 16. 17 ; XHV, FIGS 6-11, 23, 32. 



Shell elongate-ovate, valves convex, regular. Pedicle-valve with umbo 

 moderately full and beak incurved ; foramen generally concealed at maturity. 

 Cardinal slopes concave and well delimited by divergent cardinal ridges. Dor- 

 sum more or less distinctly ridged in the umbonal region, broadly convex ante- 

 riorly 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, pp. nov. 



PLATE XLII, FIGS. 1-fl. 



Shell subpentahedral in outline, transverse, rarely elongate. Valves sub- 

 equally convex, with broad, low fold and sinus developed on the anterior por- 

 tion 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, 17 mm.; 

 greatest width, 19 mm. 



Upper Silurian. Porrij countij, Tennessee. 



Zygospira putilla, sp. nov. 



PLATE LIV, FIGS. 35-:)7. 



Shell small, elongate-suboval in outline. Pedicle-valve the more convex ; 

 umbo narrowed, apex acute, delthyrium unclosed. Medially this valve is ele- 

 vated by a strong double plication, the parts of which diverge anteriorly, leaving 

 a flat, low depression between them, and in this lies a single faint plication. 

 The lateral slopes are considerably depressed, and each bears from four to 



