PLATE LIV— Continued. 



Subgenus CATAZYGA, s.-gen. nov. 



ragclM. 



C'atazvga Headi, Billings. 



Figs. 24-26. Dorsal, profile and cardinal views of the exterior ; showing the biconvex valves, the tine plica- 

 tion of the exterior and the median depression on the brachial valve. Natural size. 



Hudson River groui). Near Ottawa, Canada. 

 Figs. 28, 29. Dorsal and jirofile views of anothei' specimen. 



Hudson River group. Wear Cincinnati, Ohio. 

 Fig. 30. The intei-ior of a portion of the pedicle-valve ; showing the deep musculai- scar. 



Hudson River group. Waynt.wiUe, Indiana. 



Catazyga Headi, v:ir. borealis, Billings. 

 Fig. 27. A dorsal view of a rather large specimen of this variety. 



Hudson River gi-oup. Waynesville, Indiana. 

 Figs. 31, 32. Dorsal and profile views of a smaller shell. 



Anticosti group. Island of Anticosti. 



Catazyga Headi, var. Anticostiensi.s, Billings. 

 Fig. 33,34. Ventral and dorsal views of the exterior; showing the outline, contour and tine surface 

 plication. 



Hudson River group. Collingwood, Ontario. 



Genus ZYGOSPmA, Hall. 



Page !5t. 



Zygospira putilla. sp. nov. 

 Figs. 35-37. Dorsal, profile and ventral views of the exterior of an avei-age example. X 2. 

 Hudson River group. Near Edgewood, Pike county, Missuwi. 



Genus CYCLOSPIRA, gen. nov. 



Page 116. 



CvcLOSPiRA bisulcata, EniDions. 



Figs. 38-40. Doi-sal, piofile and vential views of the exterior of a specimen bearing a marginal plication in 

 the sinus of the brachial valve. X 2. 



Ti-enton iiuiestoue. Watertown. N. T. 



Genus DAY I A, Davidson. 



Page 62. 



Dayia navicula, Sovverby. 

 Figs. 41-43. Dorsal, frontal and profile views of an avei-age example, enlarged. 

 Fig. 44. A restoration showing the character of the spirals and loop. 



Figs. 45, 46. Enlarged translucent preparations of the spiials ; showing the lateral direction of the apices 

 and the fimbriation of the sjiiral coils. (Davidson.) 

 Ludlow shales. Shj-opshire, England. 



Genus PKOTOZYGA, gen. nov. 



I'age 151. 



Protozyga exigua, Hall. 



Figs. 47, 48. Ventral and dorsal views of a specimen ; showing the naviculate contour and smooth exterior. 

 Shells of this sjiecies usually bear one or two low, broad marginal folds on each side of the 

 median axis. X 2. 



Trenton limestone. Watertown, N. T. 



