PALEOZOIC TIME — LOWER SILURIAN. 



507 



length of 10 or 12 feet. They were the largest and most powerful animals 

 of the seas ; but they must have been much encumbered in locomotion by 

 the long bulky shell. 



656-669. 



Bkachiopods. — Figs. 656, 65T, Orthis (Platystrophia) biforata ; 658, O. occidentalis ; 659, O. testudinaria ; 660, 

 O. tricenaria ; 661, Leptana (Plectambonites) sericea ; 662, Leptiena rhomboidalis ; 663, Strophomena (Eafi- 

 nesguina) alternata ; 664-666, Ehynchonella capax ; 667, 667 a, Cyclospira bisulcata ; 668, Schizocrania filosa ; 

 669, Liugula quadrata. Figs. 656-666 from Meek ; 667-669, from HaU. 



670-682. 



Lamelmbeah-chs. — Fig. 670, Pterinea Trentonensis ; 671, Ambonychia bellistriata; 672, Tellinoinya nasuta. 

 Gasteopods. — Fig. 673, Raphistoma lenticulare; 674, Murchisonia Milled ; 675, M. bellicincta ; 676, Helicot- 

 oma planulata; 677, 678, Belleropbonbilobs tus; 679, Cyrtolites compressus ; 680, 681, C. (?) Trentonensis; 

 682, a, 6, Conularia Trentonensis. Figs. 670, 671, 677-682, Hall ; 072, Billings ; 673, 675, Meek ; 674, 676, Salter. 



