1 to 8. 
1 and 2. 
3 and 4. 
Figs. 
5,6 and 7. 
8. 
Figs. 9 to 26. 
9, 10 and 11. 
12. 
138 and 14. 
15, 16 and 17. 
18 and 19. 
20, 21, 22 and 23. 
24 
25. 
Figs. 26 to 29. 
26 and 27. 
28 and 29. 
Figs. 30 to 34. 
30, 31 and 32. 
33. 
34. 
Figs. 35 to 37. 
Figs. 38 to 41. 
38, 39 and 40. 
41. 
Figs. 42 to 44. 
42, 43 and 44. 
Figs. 45 to 48. 
45 and 46. 
47. 
48. 
Figs. 49 to 54. 
49 and 50. 
51 and 52. 
53. 
54. 
Figs. 55 to 58. 
55 and 56. 
57 and 58. 
Figs. 59 to 64. 
59 and 60. 
61. 
62 and 63, 
64, 
PLATE XXXIV. 
RELYAN CHOTREMAUAENS GEE DMIN EVs IWVAINICHELLpoyersrerey-teleeie nie creisiaisisieierelererelsy teteieeeie Inve eteiniatete 
Views of the dorsal and ventral valves of a typical example. 
Profile and anterior views of the same specimen. Near Lanesboro, Minn. Min- 
nesota Geological Survey collection. 
Dorsal, ventral and profile viws respectively of an immature specimen, x 2. 
The same specimen, natural size. Trenton shales, Minneapolis, Minn. Minne- 
sota Geological Survey collection. 
RECN CHODRENA IN:AQOULVAT Vis (CAStelMal ‘yecjerrsicie a cieielcrcicisimeeisecieiennicais etetente = 
Dorsal, ventral and profile views respectively of a specimen from the Trenton 
limestone and approaching R. orientalis Billings. x 2. 
A view from the dorsal valve of a strongly lamellose variety of this species 
occurring in the Clitambonites beds, x 2, St. Paul, Minn. 
Ventral and profile views of the same specimen, natural size. 
Three views, a ventral, dorsal and profile respectively, of another variety found 
in the middle third of the Trenton shales. Collection of C. Schuchert. 
Two views, ventral and profile, of a thin immature specimen. Fountain, Minn. 
Dorsal, ventral, profile and anterior views respectively of a large but typical 
specimen of this species. Trenton shales, Minneapolis, Minn. Minnesota 
Geological Survey collection. = 
An interior view of the ventral valve showing the muscular scars and teeth, x 2. 
The interior of the dorsal valve to show the crural plates, linear cardinal pro- 
cess and the adductor muscular scars. Near the top of Trenton limestone, 
Burgin, Kentucky. Collection of C. Schuchert. 
IND QUDVALVAS Van. ATTIC OSAMA Wy AMG! S\fetstersistelsieis stelsielessicjateelee)cre ere ele eislereis/sie1= 
Dorsal and ventral views of a very characteristic specimen showing the prom- 
inent lateral coste. 
Profile and anterior views of the same specimen. The latter shows the flattened 
anterior margin, which is often well developed in this variety. Galena shales 
near Cannon Falls, Minn. Collection of C. Schuchert. 
REYNCHOLREMAY CAPA (CONTAC WS pranciicrlsaccrtescis een cane eae eesti cei eee 
Three views of a large matured specimen. 
A broken dorsal valve, showing the crural plates surrounding the cardinal 
process, the prominent mesial septum and the adductor scars on each side of 
it. Hudson River group, Spring Valley, Minn. Minnesota Geological Survey 
collection. 
The interior of a very thick ventral valve. Hudson River group, Iron Ridge, 
Wisconsin. Minnesota Geological Survey collection. 
IRE YNCHONELIGA 2. NENCATER |W GL OO sjepscreie-/-tetereisteverere) usietelaleieleieistenersioisieletciusteletereieers 
Dorsal, anterior and profile views of the type specimen. 
(After Whitfield.) 
Hudson River group, Dejafield, Wisconsin. 
ZVGOSPIRAL RECUR VIROSTIRAG Hall eS s ecer c-tleeintetercmesaci oeicieeeeiechiseriem amici 
Three views of a typical example of this species. 2. Galena shales near 
Cannon Falls, Minn. Minnesota Geological Survey collection. 
A specimen filled with crystalline calcite, showing the spirals and the connecting 
band. The latter is drawn wrongly, the point of attachment of the loop is 
nearer the anterior recurved portion of the primary lamellae. x4. Collection 
of C. Schuchert. 
ZX. GOSEIR-AGMODES TAN (SayeviSs) velalll eee ene eeiiseecineee-iiceic cecil aaterereieerriots 
Dorsal, ventral and profile views respectively of a specimen in which the sinus 
and fold are not so prominent as in Ohio valley specimens. Hudson River 
group, Spring Valley, Minn. Collection of C. Schuchert. 
LS.GOSP TRAY UPR VAM Wie GUS ayerac(areeieterisieierroeisereisi ers aalatciolasyacacietecin ter tmeree eit 
Ventral and profile views of a typical example. x 
‘View from the dorsal valve of the same specimen. x 2. 
View of a natural cast of the ventral valve, showing the muscular area and the 
diverging vascular sinuses. ~* 2. 
CXCHOSPIRAGEISUL CATA HMMMONS WS Daeerarererienceceacrtieimetioictcecietelsterseiiseetets 
Views from the dorsal and ventral valves of an ordinary specimen. x 2. 
Profile and anterior views of the same specimen. X 2, 
Natural size view of the same specimen. 
A specimen filled with crystalline calcite, preserving the sickle-shaped spiral 
bands and the connecting band. x4. Collection of C. Schuchert. This draw- 
ing has the recurving portion of the primary lamellx entirely too divergent, 
while the loop should be more posteriorly or midway between the present 
position and the point of origin of the brachial supports. 
EVAL LENA SAB MOR DT AVViotQll Gh Siar. sierercmelstacterreroie sia siete icici Cereer eieisrsteieintetelerarsicis'creielatalete 
Dorsal and ventral views of the type specimen. * 4. 
Dorsal and proiile views of the calcareous arm supports. 
stone, Lebanon, Tennessee. Collection of C. Schuchert. 
EVA EENAG NICOLE ETD sWissAll Gi Sieveriott-rerestiendesiieiteeves terete eterommerersiekersrereieieeie als lore cers 5 
Two views of the common form of this species. x 4. 
Outline drawing to show the nature of the loop of the species. 
Opposite views of a large and more strongly plicated specimen. x 4. 
Outline profile view of the preceding. ‘Trenton limestone, Fountain, Minn. 
Collection of C. Schuchert. 
x4. Glade lime- 
459 
461 
462 
465 
466 
468 
473 
474 
