PLATE LXXX. 
(Figures 1-17, 23-35 by 11. P. Whitfield; 18-22, 36-39 by E. Emmons.) 
Genus CEYPTONELLA, Hall. 
Page 286. 
Cryptonella rectirostra, Hall. 
Figs. 1-3. Dorsal, ventral and profile views of a small shell with characteristic outline. 
Fig. 4. Dorsal view of a large, somewhat distorted specimen, retaining the deltidial plates. 
Hamilton shales. Canandaigua Lake, Neto Y<rrk. 
Cryptonella plamrostra, Hall. 
Fig. 5. Dorsal view of an average specimen retaining the deltidial plates. 
Figs. 6, 7. Dorsal and profile views of a large and much thickened shell. 
Hamilton shales. Western New Ywk. 
Figs. 8, 9. Ventral and doi'sal views of an internal cast; showing the muscular impressions and vascular 
sinuses. 
Hamilton group. Hardjg county, Virginia. 
Fig. 10. An enlargement of the cardinal portion of the pedicle-valve ; showing the foramen, deltidial plates 
and teeth. 
Hamilton group. Moscoio, New Yoi’k. 
Cryptonella eximia, Hall. 
Fig. 11. Profile view of a somewhat gibbous shell; showing the contour of the valves. 
Fig. 12. An enlargement of the umbonal portion of the valves ; showing the foramen, deltidial xilates and 
cardinal slopes. X 3. 
Lower Helderberg grouj^. The Helderhm-gs, New York. 
Subgenus CKANHSNA, s.-gen. nov. 
Page 297. 
CRANiENA Romingeri, Hall. 
Figs. 13-15. Dorsal, ventral and profile views of a typical example; showing the median sinus on the 
pedicle valve and the anterior emargination. X 2. 
Figs. 16, 17. The loop of this species, greatly enlai'ged ; showing the divergence of the descending branches, 
their short recurvature, and the conspicuous crural apophyses. 
Hamilton group. Thunder Bay, Michigan. 
Figs. 18, 19. Dorsal and ventral views of a somewhat broader foi m. 
Hamilton group. Iowa City, Iowa. 
Genus DIELASMA, King. 
Page 293. 
Dielasma Calvini, Hall and ^Vhitfield. 
Figs. 20-22. Dorsal, profile and ventral views of a mature individual; showing the form and contour of the 
valves and retaining the foramen and deltidial plates. 
Hamilton group. New Buffalo, lo^ca. 
Subgenus EUNELLA, s..gen. nov. 
Page 290. 
Eunella Sullivanti, Hall. 
Fig. 23. An enlarged view, showing the loop. X 3. 
Corniferous limestone. Cayuga, Ontaiio. 
Figs. 24-26. Dorsal, ventral and profile views of one of the original specimens, 
Corniferous limestone. Columbus, Ohio. 
