PLATE, L— Contiiiueil. 



Subgenus HOMCEOSPIRA, s.-gen. nov. 

 HoMCEosriUA sonuiNA, Becchor aiitl Chuke. 



Fig. 26. A ventral view of an individual of about average size. 



Figs. 27, 28. Pi-otile and dorsal views; showing the convexity of the valves an<l the character of the plica- 

 tion and concentric ornamentation. X 2. 



Niagara group. JValdro7i, Indimia. 



Genus HHYNCIIOSPIRA, Hall. 



rage 108. 



Rhynchospira Electra, Billings. 



Figs. 29-31. Dorsal, ventral and jiroKle views of the oiiffinal specimen. 

 Lower Helderberg group. Square Lake, Maine. 



Subgenus H0M(E0SPIRA, s. gen. nov. 



I'affc Hi. 

 IIoJIOiOSriKA (cf.) EVA\, Hull. 

 Fig. 32. A dorsal view of an average specimen ; showing the character of the deltidial plates and the sur- 

 face plications. X 2. 

 Fig. 33. The interior of a pedicle-valve. 



Fig. 34. The intericn- of a brachial valve ; showing the hinge-plate and median septum. X 2. 

 Fig. 35. The cardinal portion of the last specimen, enlarge<l to show in more detail the structure of the 

 hinge-plate. X B. 



Upper Silurian. Perry county, Tennessee, 



Genus TRIGERIA, Bayle. 



Pa^e 265. 



Trigeuia lepida, Hall. 



Figs. 3G-3S. Doi'sal, ventral and profile views of a typical specimen ; showing the character of the exterior 



and the form of the deltidial plates. X 2. 

 Fig. 39. A dorsal view of a more elongate shell, with a pronounced median sinus on the brachial valve. X 2. 

 Fig. 40. An enlargement of the umbunal i-egion of the specimen represented in tig. 36 ; showing the delti- 

 dial plates, the form of the foramen and its encroachment upon the apex of the valve. X •). 

 Hamilton group. Canandaiyua. Lake, N. Y. 

 (The lithographing of this plate was completed before the discovery of the fact that this species 

 is a terebratuloid allied to Rens.sel^ria, and referable to the genus Tkigekia, Bayle, as inter- 

 preted in this work.) 



Genus RHYNCHOSPIRA, Hall. 



Page 108. 



Rhynchospika (?) Eugenia, Billings. 

 Figs. 41-43. Dorsal, ventral and profile viewsof aspec-imen; showing the usual form of exterior at this locality. 

 X 2. Hamilton group. Yor/c, iV. ¥. 



Rhyxcho.spira (?), .•?p. 

 Fig. 44. A view of the exterior of a jiedicle-valve, the only specimen of the species observed, and referred 

 to this genus with doubt. 



Waverly gi-oup. Northwestern Pennsylvania. 



Rhynchospika scansa, sp. nov. 

 Fig. 45. A view of the exterior of a pedicle-valve ; showing a median sulcus similar to that occurring in 

 the typical representatives of the genus. 



Waverly group. McKean county, Pennsylvania. 



Genus CAMAROSPIRA, gen. nov. 



Page 8-2 



Camarospira Eucharis, Hall. 



Figs. 46, 47. Dorsal and ventral views of the exterior. The position of the me<Iian septum is seen through 



the shell-substance on each valve. 

 Fig. 48. A profile view ; showing the convexity of the valves. 



Corniferons limestone. Cass county, Indiana. 

 Fig. 49. A dorsal view of the original example of Caiiiarojjli-oria Eucharis ; showing a rather more pro- 

 nounced median fold on the t)rachial valve. 

 Fig. r.O. A ventral view of a specimen broken so as to expose the spondylium of the pedicle-valve. 



Corniferous liniestone. Cayuga, Ontario. 

 Fig. 51. A median longitudinal section; .showing the spondylium and supporting septum of the pedicle- 

 valve and the septum of the bi'achial valve. X li 

 Fig. 52. A transverse section in the umbonal region ; showing the spondylium and septa. X 1^. 

 Cornifei'ous limestone. Cass county, Indiana. 



