Kina tomo. 
and 2. 
Figs. 4and 5. 
4. 
5. 
Figs. 6and 7. 
6. 
ths 
Fig. 16 
16 and 17. 
Figs. 
Figs, 22 to 24. 
22 and 23. 
24. 
Figs. 
26. 
27 and 28. 
Figs. 35 to 37. 
35 and 36. 
37. 
s. 12 and 13. 
s.14 to 17. 
14 and 15. 
18) to, 21: 
18 and 19. 
20. 
21. 
25 to 29. 
PAN 
s. 30 and 31. 
s. 32 to 34. 
32 and 33. 
34. 
PLATE XXxXI. 
PAGE. 
STR OLHOME NAGS ED AUTUAU VV) GUIVC iiSiateseisieleratsletasclotetetialefevalstalayatan sketen-felaisteietstotelfetatetetenteeeia tote 390 
Dorsal and profile views respectively of the same specimen. 
Interior of the ventral valve, to show the long median septum of this species. 
Trenton shales, St. Paul, Minn. Collection of C. Schuchert. 
STROPHOMENA RUGOSA (Rafinesque Ms.) Blainville..................eeeeeeeeeeees 390 
Interior of the ventral valve. The septum of the muscular area does not extend 
to near the anterior margin, as in S. septata. 
Interior of the dorsal valve. Hudson River group, Oxford, Ohio. 
C. Schuchert. 
STROPHOMENA NEGLECTA, Var. ACUMA, MY VALs ««cisiec 2s = ale sice/seisaeielsje jac stelle 5 cl'= 
A view of the dorsal valve, to show the oblique wrinkling along the hinge line 
and distinct alternation of the strie. 
Profile outline of the same specimen. 
Collection of C. Schuchert. 
STROPHOMENA PLANODORSATA W. and S.. 
A dorsal view of the largest specimen seen, somewhat restored. The outline of 
smaller individuals is more like that of fig. 10. 
Profile outline of same specimen. Hudson River group, Spring Valley, Minn. 
University of Minnesota collection. 
Interior of a ventral valve referred to this species. 
ton, Illinois. Collection of C. Schuchert. 
STPROPHOME NAW SVIN CEDE TE Usl et cy rege etryeyetetstel state te tonelePalayatetalelecletaleetelclereielecelststelstelaletetsiststel 
A view of the dorsal valve of this species. (After Hall.) Lower Blue beds of 
Wisconsin. 
Collection of 
Hudson River group, Spring Valley, Minn. 
Hudson River group, Wilming- 
STROPHOMENA TRILOBATA Owen, 
Dorsal and profile views of a specimen showing the small, flat corrugated visceral 
disc, and the long median extension. Middle Galena, Old Concord, Minn. Col- 
lection of C. Schuchert. 
SRROLHOMEN AB HL UCLUOSAME IMI GS peieteerlatermietelertlslletstelapeietfelstelaietcaciatoleyetaichetelieteletcieiteets 
Dorsal and profile views of a specimen intended to show the strongly wrinkled 
visceral disc. 
The interior of a ventral and a dorsal valve respectively. Hudson River group, 
Spring Valley, Minn. Collection of C. Schuchert. 
STROPHOMENANSCORMETD Inv) 10 Cas aciereteey-telefarteteiiaielereetelersieities etal ceieieieiseietsterteier teeter 
Dorsal and profile views of a specimen of the usual size of this species. 
An interior of the dorsal valve. Minnesota Geological Survey collection. 
Interior of the ventral valve. Galena shales, near Cannon Falls, Minn. 
tion of W. H. Scofield. 
STOR HOMEN AWE MUA CUACVAY IVs CUT) ClitssivereretncrateeteleleloceleiepelTeeteel-ietereintstelclejoteinictelsieceeielatersteters 
View of the ventral valve, natural size, and a profile of the same specimen, x 2. 
View from the dorsal valve, x 2. Galena shales, near Cannon Falls, Minn. Col- 
lection of W. H. Scofield. 
RAFINESQUINA MINNESOTENSIS N. H. Winchell.... ....... 12... .cceceeceweeeees 
View of a natural cast, one of the type specimens, of the ventral valve as. pre- 
served in the Trenton limestone, Minneapolis, Minn. Minnesota Geological 
Survey collection. 
Profile view of a specimen from the Trenton shales, St. Paul, Minn. 
of C. Schuchert. 
ViALICUVAIN QUIASS Ata SAN CSO Ulneytetcyeyreteieteleve lee totenetersiaeteloielelevsteleteloletaatete lotsa etal -tstelstelereiteteteeets 
Dorsal and profile views respectively of a specimen of the ordinary size of this 
species as it occurs near the base of the Upper Buff beds at Mineral Point, Wis. 
Minnesota Geological Survey collection. 
Interior of the dorsal valve, showing the tive characteristic septa of this species. 
(After Hall.) 
RAFINESQUINA DELTOIDEA Conrad, sp. 
Views of a natural cast of the interior of the ventral valve and a profile of same. 
Middle Galena, Mantorville, Minn. Minnesota Geological Survey collection. 
RAFINESQUINA ALTERNATA (Conrad Ms.) Emmons, sp... 
A ventral and a profile view of this species as it occurs in the Galena shales in 
Goodhue county, Minn. Minnesota Geological Survey collection. 
Interior view of a thick dorsal vavle in which the various parts are strongly 
deyeloped. Trenton shales, St. Paul, Minn. Collection of W. H. Scofield. 
R. ALTERNATA, Val. LOXORHYTIS Meek, Var... secs ev eecnccccresiewsevseresscescs 
View of the ventral valve and a profile outline of the same specimen, ‘to show the 
great convexity and transversity of this variety. Collection of C. Schuchert. 
Interior of the dorsal valve. Hudson River group, Spring Valley, Minn. Min- 
nesota Geological Survey collection. 
Collec- 
Collection 
388 
393 
394 
398 
399 
401 
403 
403 
404 
