PLATK LIV—Continued. 
^ SuHOENUs CATAZYGA, s.-gen. nov. 
Page,157. 
Catazyga Headi, Billings. 
Figs 24-26. Dorsal, profile and cardinal views of the exterior; showing the biconvex valves, the fine plica¬ 
tion of the exterior and the median depression on the brachial valve. Natural size. 
Hudson River group. Near Ottawa, Canada. 
Figs. 28, 29. Dorsal and profile views of another specimen. 
Hudson River group. Near Cincinnati, Ohio. 
Fig. 30. The interior of a portion of the pedicle-valve ; showing the deep muscular scar. 
Hudson River group. WayntsviUe, Indiana. 
Catazyga Headi, vtii-. borealis, Billings. 
Fig. 27. A dorsal view of a rather large specimen of this variety. 
Hudson River group. Waynesville, Indiana. 
Figs. 31, 32. Dorsal and profile views of a smaller shell. 
Anticosti group. Island of Anticosti. 
Catazyga Headi, v;ir. Anticostiensis, Billings. 
Fig. 33, 34. Ventral and dorsal views of the exterior; showing the outline, contour and fine surface 
plication. 
Hudson River group. Collingwood, Ontario. 
Genus ZYGOSPIRA, Hall. 
Page 15t. 
Zygospira putilla, sp. nov. 
Figs. 35-37. Dorsal, profile and ventral views of the exterior of an average example. X 2. 
Hudson River group. Near Edgewood, Pike county, Missouri. 
Genus CYCLOSPIRA, gen. nov. 
Page U(5. 
Cyclospira bisulcata, Enuiions. 
Figs. 38-40. Doi'sal, profile and ventral views of the exterior of a specimen bearing a marginal plication in 
the sinus of the brachial valve. X 2. 
Ti’enton limestone. Watertown, N. Y. 
Genus DAYIA, Davidson. 
Page 62. 
Dayia navicula, Sowerby. 
Figs. 41-43. Dorsal, frontal and profile views of an averag-e example, enlarged. 
Fig. 44. A restoration showing the character of the spirals and loop. 
Figs. 45, 46. Enlarged translucent preparations of the spirals; showing the lateral direction of the apices 
and the fimbriation of the spiral coils. (Davidson.) 
Ludlow shales. /Shropshire, England. 
Genus PROTOZYGA, gen. nov. 
Page 151. 
Protozyga exigua, Hall. 
Figs. 47, 48. Ventral and dorsal views of a specimen ; showing the naviculate contour and smooth exterior. 
Shells of this species usually bear one or two low, broad marginal folds on each side of the 
median axis. X 2. 
Trenton limestone. Watertown, N. F. 
