CORRELATION OF STRATA. 
Hudson or 
Trenton Period. paca 
Stones Black Trenton 
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Strophomena winchelli Hall............. 394 ‘realpait 
Strophomena trilobata Owen............ 395 x 
Strophomena fiuctuosa Billings.......... 395 |} ae 
Strophomena billingsi, n. sp............. 397 x 
Strophomena scofieldi W. &S............ 398 x 
Strophomena emaciata W. &S..... ...- 399 x 
Rafinesquina minnesotensis N. H. Winch.} 401] x | x 
Rafinesquina ‘‘ var. inquassa Sardeson.} 403 x x 
Rafinesquina deltoidea Conrad........... 403 ? x 
Rafinesquina alternata Conrad........... 405 3 || 5x ||) Be if 
Rafinesquina ‘‘ var. loxorhytis ? Meek.} 407 x 
Eriplecianwlrichiy na Sp) ececseeiieacee: - 409 axe 
Leptena charlotte W.&S.............. 410 xe || sz |] 
-Leptena unicostata M. & W............. 411 12 || Bs 
Plectambonites sericea Sowerby......... 414) x 29 || 2% |) s% J} ae]! ox jl Ss x |x 
Plectambonites preecosis Sardeson sp.... x 
Plectambonites gibbosa W. &S.......... 416 5x 
Orthis tricenaria Conrad................. 418} x| x| x] x] x|]x]x/x 
O. (Dinorthis) deflecta Conrad........... 422) x | x 
O. (Dinorthis) pectinella Hmmons....... 424 fe 
O. (Dinorthis) ‘‘ var. sweeneyi N. H. W.} 426 if 
O. (Dinorthis) meedsi W. & S............ 427 x 
O. (Dinorthis) “ var. germana W. &S.} 428 n 
O. (Dinorthis) subquadrata Hall......... 428 x 
O. (Dinorthis) proavita W. &S........... 431 x 
O. (Hebertella) borealis Billings......... 433 x 
O. (Hebertella) bellarugosa Conrad.......] 434] x | x x Xs x 
O. (Hebertella) insculpta Hall........... 435 x 
O. (Plectorthis) plicatella Hall........... 436 xe || Se 
O. (Plectorthis) whitfieldi N. H. Winch. .} 437 x 
O. (Dalmanella) hamburgensis ? Walcott] 440 x 
O. (Dalmanella) testudinaria Dalman....} 441 x¢|| 5x || 3 xe || 3 
O. (Dalmanella) tersa Sardeson.......... x 
O. (Dalmanella) subeequata Conrad...... 446] x | x| x 
O. (Dalmanella) “ var. conradi N. H. W.} 449] x | x 
O. (Dalmanella) “ var. perveta Conrad..} 450 Xe |} 3s |] xe 
O. (Dalmanella) “ var. gibbosa Billings.] 451 x 
O. (Dalmanella) “ var. circularis N.H.W.} 452 xd 
Platystrophia biforata Schlotheim....... 455 x |x x 
Platystrophia crassa James.............. 458) x 
Rhynchotrema minnesotensis Sardeson. . x¢ || 5 |) &S || x 
Rhynchotrema ainsliei N. H. Winchell. .| 459 x| x 
Rhynchotrema insequivalvis Castelnau..}| 459 x] x] x 
Rhynchotrema “ var. laticostata W. &S.| 461 x 
Rhynchotrema capax Conrad............. 463 ? x 
Rbynchonella (?) anticostiensis Billings.] 464 tT 
Rhynchonella (?) neenah Whitfield....... 465 if 
Zygospira recurvirostra Hall............. 466 ><] BS] |i ||| se) eel | Se) Bie 
Zygospira modesta Say...........-.e000- 467 x< || Sx 
Zygospira uphami W. &S................ 468 x 
Zygospira (Hallina) nicolleti W. &S..... 469] X | x 
Cyclospira bisulcata Emmons............ 470 x 
LAMELLIBRANCHIATA. 
Ambonychia planistriata Hall........... 491] x | ? 
Ambonychia bellistriata Hall............ 492 x 
Ambonychia affinis, n. sp ............... 492 x 
Ambonychia amygdalina Hall........... 493 x 
Clionychia lamellosa Hall............... 494 xe 
Clionychia nitida, n. sp.........+2+...... 495] X 
Clionychia erecta Hall................... 496 as 
Clionychia rhomboidea Ulrich............ 496] x 
Clionychia undata Emmons.............. 497 x], 
Byssonychia intermedia M. & W......... 499| x}: 
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