Figs. l to 5. 
land 2, 
3 and 4. 
5. 
Figs. 6 to 8 
6. 
Zand 8. 
9 to 14. 
9 and 10. 
Figs. 
il and 12. 
13 and 14, 
Figs. 15 and 16. 
Figs. 17 and 18. 
Fig. 19, 
Higs. 20 to 
20 to 
Figs. 26 to 28. 
26 and 27. 
28. 
Fig. 29. 
Fig. 30. 
Figs. 31 to 33. 
31 and 32. 
33. 
Figs. 34 to 36, 
Fig. 37. 
Figs. 38 to 40. 
38. 
39. 
40. 
Figs. 41 to 43. 
41 and 42. 
43. 
Figs. 44 to 49. 
44, 
45 to 47. 
Figs. 50 to 
Figs. 53 to 
53 to 
57. 
58. 
PLATE XLII. 
PAGE. 
PGR ODE SMAGEACUSEUN AT UM MAGE SD tise rariiminete sieves eleaetare eee ec sicireait cea coxieiasicta ein aie sists Zibsat afelsipitiaetp-eisieislalsi sa = prasaiele 609 
Lateral and cardinal views of a large right valve of the typical form. 
Opposite views, the inner X 2. of a left valve of the var. intermedia 
The hinge of a right valve of the typical form, x 3, showing the retral sweep of the teeth. 
PAHO DMSMAS CANNONENSE Bilct SME enht Else acini alee cieiselerasoistbiciseinnciacisacnaunalahincia suns ain along res cccisss sles clsatdalridee's 910 
Somewhat weathered cast of the interior. 
Lateral and cardinal views of a cast preserving the muscular scars. 
ALLODESMA SUBELLIPTICUM Ulrich ma 617 
Cardinal and lateral views of the cast of the interior upon wrinetarn the recess was founded. 
Lateral and cardinal views of a better preserved cast, X 2. showing the muscular sears, pallial line 
and impressions of the hinge teeth, 
Restoration of the hinge. 
MO DIOROPSTSHOWHNim Os S Dimetectee sett te attae ere taeistemisreimerce an iuleiameisse siete iste -eicestees tote statefalniite = nfvia sintatainaicie «ir vieietmletdieisie 
Lateral and cardinal views of a partial cast of the interior. 
MODIOLOPSIS: CONSIMIMISsam ay SD tier (ae ems sone sick odes sinc cies steele eet sate lsilecieleieis/ eine stocise at bs cas Sone Oseaneeod 
Lateral and cardinal views of an entire silicified example of this species. 
MODIOLOPSIS SIMILIS Ulrich .........-.-....- =erele eBidh ane sadioseO ECan No beae Bods bouAO LOSUCCO> 
(See also walenia 5 SSSR: eet 1 and 2 2, ) 
View of the right side of the type of this species. The specimen is preserved chiefly as a cast of the 
interior and shows an impression of the shallow anterior muscular scar. 
OLMOPHORUSINNGLEOMUS tba Weert ere eel er ee iateycleleelmieie intel) se tatsicietee lo sctebeaiakelatebey lala aie rinie/a\ctelolstcinientsi<i= oe oo0308 
Four views of a rather large specimen from the left side of which the shell has been removed, so as to 
show the muscular sears and the strong vertical furrow left by the clavicle. The posterior extrem- 
ity in this specimen is narrower than usual. 
An oblique cardinal view of a cast of the interior, x 6, showing an impression of the denticulated hinge. 
Very perfect cast of the interior of an unusually large right valve, showing, besides the usual char- 
acters, several obscure rays on the sides and a number of small umbonal scars. Minn. Geol. Sur. 
Mus. Reg. No. 7336. 
OUENODONTAGLOGAINT: Sal ter ise ulin cy meee nse Mean nN anni ln: Baoan, tae son jan aaee RCE coh law stes 
‘Cast of the interior of a right valve. Minn. Geol. Sur. Mus. Rees No. 8316. 
Gutta-percha impression of same, Showing the hinge. 
CTENODONTA OVIFORMIS, N. SP.......0.. eee cee eeee ences veers Habeas Be peotos So0e0 
Left side of a cast of the interior, showing the strong ryameroulla § scars sland DRG. characters: of the 
species. 
CTENODONTA NASUTA Hall........... ....e.eeeeeees AGndodedabseeebSa Uap boauopeddansnp Ucdo cope Scecponbtapdog coBte. 
A small testiferous left valve of this species from the middle third of the Trenton shales, near Cannon 
Falls, Minnesota. 
OTENODONTAN CUNEIRORMIS) nies Die-ce nee corisces eciniccntien ites ale cisersinl em clstete ciefeelse = siatialsloh-tsimisfaeisieieisiniel= lasfmiate tsa 
Two right valves, the first with the posterior constriction more distinct than in the other. 
Hinge of a right valve, x 2. 
CTENODONTA SUBNASUTA, 0. SD...... Bee aa coe aotra SG RREE aaa ee erie gmieee Se oan SoBe Boies Seay Beso r ONT ROOAOS 
Three views of a cast of the interior. 
CTENDONTA GIBBERULA Salter.. ae san 
(See Bice hort a "599, fig sth a eal =) 
An excellent mold of the interior of a left valve. 
CTENODONTA PLANODORSATA Ulrich........ 
(See also plate xxxvQ, figs. 25—28 ) 
View of the inner side of a left valve, x 3. 
Hinge of same, more highly magnified. 
Artificial cast of the interior of a right valve. 
OTENODONTANC ARENA TAG Mi SD, b= Acswane rca ccietettesls piel alice: sn NS Suceee | ebiadicat) ava aalswiogtcts = elcwelnw cites we 
A right and left valve, both imperfect and varying sligtly in outline. 
Dorsal view of the left valve, 
OPENODONTA NIT AAU TIC Hes aaj pssaahe tet semaines Meni nak sos Ssae cee Qous Jo ssecdgas eden baocadeenokqnoasdocoo con 
The right side of a small testiferous specimen. « 
Lateral, cardinal and posterior views of same, X 2. 
The right side of a well preserved cast of the interior of a large example. 
Cardinal view of same, X 2, showing sears of the adductor and pedal muscles, 
OTENODONDAYBTE DDATIES hy MINS Dies -nisrey seks Noratnice oe he rineie sta aac ee alae eae ecole ovate ae nanicio nlalele Seba nee 3 
Silicified right valve of the species from the middle third of the Trenton shales. 
Hinge of same, X 2. 
Cast of the interior from the Galena shales, provisionally referred to this species. 
ODENODONTA:SCORTEEDE, geiS Diese aries cee ase isiels aie eet meee Pe eee ah eae a nseisantea seeinie at weesciec talks 
The left side and posterior, anterior and dorsal views of a specimen preserving the shell and showing, 
among other characters of the species, the sharply angular umbonal ridge. Middie third of the 
Trenton shales, near Cannon Falls, Minnesota. 
Hinge of a right valve, x 2. 
The right side of a cast of the interior from the Galena shales, provisionally referred to this species. 
The anterior end is larger than in the typical form. 
(OVER. 
505 
504 
607 
59L 
584 
587 
585 
587 
589 
589 
592 
593 
593 
