502 



HISTORICAL GEOLOGY. 



1. Molluscoids. —Fig. 630 shows a branching coral-like species of Br3^ozoan, 

 Sulcopora fenestrata H., and Fig. 629 one of the reticulate kinds, Suhretepora 



627-638. 



01^:^ (jr.. 629 ^.ii?;^ 



689. 



Ceinoids. — Fig. 62T, Pal»ocrinus striatus; 628, Malocystites Murchlsoni. Molluscoids. — 629, Suhretepora 

 incepta; 680, Sulcopora fenestrata; 631, Orthis costalis; 632, Strophoraena plicifera; 633, Ehynchonella 

 plena. Molluscs. — 634, Maclurea magna; 635, M. Logani (x |); 635 a, operculum of same; 636, Scalites 

 angulatus; 637, Bucania rotundata. Crustaceans. — 638, Leperdltia Canadensis, var. nana. Figs. 627, 

 628, Billings; 629-634, and 636, 637, Hall; 635, 635a, Salter; 688, T. K. Jones. 



incepta H. ; and Fig. a for each is an enlarged view of the surface. Some of 

 the common Brachiopods are Orthis costalis H. (Fig. 631) , jStrophomena (?) 



p)licifera, H. (Fig. 632), and Rhynclionella plena H. 



2. Mollusks.— Figs. 634 to 637 show the forms of 

 various Gastropods ; 634 is the very abundant Mac- 

 lurea magna; it is often eight inches in diameter. 

 Fig. 635 is a view of another species which shows 

 also the operculum closing the aperture ; and 635 a 

 is the separated operculum. Fig. 637, Bucania rotun- 

 data, is related to BeMerophon. 



3. Crustaceans. — Ostraeoid Crustaceans of the spe- 

 cies Leperdltia Canadensis (Fig. 638) are common. 



Several Cambrian genera of Trilobites, Dicellocephalus and others, had 

 disappeared, Bathyurus had lost the prominence it had in the Calciferous 

 era, and the genera Illmnus, Asaphus, Ceraurus, AmpJiion, were continued 

 on with new species. Fig. 639 represents the pygidium of an Amphion. 



1. Rhizopods. — Girvanella of Nicholson and Etheridge (1878), made by them doubt- 

 ingly Foraminiferous, includes, according to its describers, Strephochetus (Figs. 625, 626) 



Amphion Canadensis. 

 Billings. 



