BRACHIOPODA. 
365 
Meristella Walcotti, sp. nov. 
PLATES XLin, FIGS. 16. 17 ; XLIV, 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, sp. nov. 
PLATE XLII, FIGS. 1-6. 
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. Perry county, Tennessee. 
Zygospira putilla, sp. nov. 
PLATE LIV, FIGS. 35-37. 
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 
