PLATE LXXX. 



(Figures 1-17, 23-35 by K. 1'. Whitkiklli; 18-22, 36-39 by K. Kmmons.) 



Genus CEYPTONELLA, Hall. 



Page 286. 

 Cryptonella KECTIROSTKA, HilU. 



Figs. 1-3. Dorsal, ventral and protile views of a amnll sliell with characteristic outline. 

 Fig. 4. Dorsal view of a large, somewhat distorted specimen, retaining the deltidial jjlates. 

 Hamilton .shales. Canandaigim Lake, New Yoi-k. 



Cryi'tonella planikostra, HmII. 



Fig. ."). Doi-sal view of an average specimen retaining the tleltidial plates. 

 Figs. 6, 7. Dorsal and profile views of a large and much thickener! shell. 



Hamilton shales. Weste)-n New York. 

 Figs. 8,9. Ventral and dorsal views of an internal cast ; showing the mu.scular impressions and vascular 

 sinuses. 



Hamilton group. Hardy coimtij, Virginia. 

 Fig. 10. An enlargement of the cardinal portion of the pedicle-valve ; showing the foramen, deltidial plates 

 and teeth. 



Hamilton group. Mo.<ivim, New York. 



Cryptonella eximia, Hall. 



Fig. 11. Profile view of a somewhat giblious shell ; showing the contoui- of the valves. 

 Fig. 12. An enlargement of the umbon.al portion of the vah'es ; showing the foramen, deltidial iilates and 

 cardinal slopet^. X 3. 



Lower Helderberg group. The Helderhergs, Ne%o York. 



SUBGENU.S CRA.NJ5NA, 8.-GEN. NOV. 

 Page 207. 



Cran^na Romingeri, Hall. 



Figs. 13-15. Dorsal, ventral and pi'ofile 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 enlarged ; 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 foim. 

 Hamilton group. Iowa Cltij, Iowa. 



Genus. DIELASMA, King. 



Page 293. 



Dielasma Calvini, Hall and VVhittield. 



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. Neio Buffalo, Iowa. 



Subgenus EUNELLA, s. -gen. nov. 



Page 290. 

 EuNELLA SULLIVANTI, Hall. 



Fig. 23. An enlarged view, showing the loop. X 3. 



Corniferous limestone. Cayuga, Ontario. 

 Figs. 24-26. Dorsal, \entral and profile views of one of the original specimens. 



Corniferous limestone. Columbus, Ohio. 



