Figs. 1 and 2. 
Figs. 3 to 6. 
3 and 4, 
5 and 6. 
Fig. if 
Fig. 8. 
Figs. 9and 10. 
Figs. 11 and 12. 
Figs. 13 and 14. 
13. 
14. 
Figs. 15 and 16. 
15. 
16 and 16a. 
Figs. 17 and 18. 
Figs. 19 and 20. 
19. 
20. 
Figs. 21 and 22. 
Figs. 23 and 24. 
Figs. 25 and 26. 
7 and 28. 
21. 
Figs. 
28. 
Figs. 29 and 30. 
PLATE XXXVI. 
MODIOLOPSIS: SIMTLIS) WITCH oo << /sfeisie a tjein ot sislep cicle eles seas 00,08 alvlel tsiclebinz b= «=e ele riens 
(See also plate xm, fig. 19.) 
Dorsal and anterior views of the original type of the species. 
the Trenton shales, Minneapolis, Minnesota. 
Middle third of 
IMODIOHOPSIS! ARGUILA, NASP. .'ela.2 sie.0 «0 pale cmc'ene cee since * cecjsine om\ssipe antes ona dea ciein 
The right side and a dorsal view of a good cast of the interior. Middle third of 
the Trenton shaies, near Fountain, Minnesota. 
A smaller testiferous specimen, imperfect posteriorly, of the natural size and x 2. 
Chatfield, Minnesota. 
MODIOLOPSIS NANA, 0D. Sp. 
Right side of a well preserved cast of the interior. 
Minnesota. 
Sere ee ee ee eee ee ee ro 
Galena shales, Cannon Falls, 
IMODIOEAPSIS  AGe TEM OLDE ELA! lerrec cic ere eefeicinis = ofa ieiriniei on ise simacie re oieisle io al ciela ninteiniats 
Cast of a left valve. Middle Galena, near Wykoff, Minnesota. 
MODIOLOPSIS CHATFIELDENSIS, ND. Sp. 
Right side of a cast of the interior, of the natural size and x 2. Middle third of 
the Trenton shales, Chatfield, Minnesota. 
MODIOLOPSISTOBSOG EIA Me: SP cjceisia cielo) fein ini ofolt iciera(ecleiniatelasts sje'ao eapicresla te Hoiinby eae 
Testiferous left valve, of the natural size and x 2. Upper part of the middle 
third of the Trenton shales, Goodhue county, Minnesota. © 
MODIOLOPSIS EX CEELENS)UaSPan fees 3\rnpte cilcip = hovel antes ose ola vies pio = ase biplane’ 
Cast of the interior of a right valve. The specimen is a little imperfect in the 
anterior third. Geol. Survey Mus. Reg. No. 8374. 
Well preserved fragment (anterior part) of a cast of the interior of a left valve. 
Survey Museum Reg. No. 8375. Hudson River group, Granger, Minnesota. 
MODIOLOESISICONCA VA UISIGDE jf ccije'id.o sopeice sue eee eerebecleemtees tone mintla cacomeiarniee 
The specimen described, a testiferous right valve, of the natural size. 
Lateral and dorsal views of same, x 2. Upper part of the middle third of the 
Trenton shales, Goodhue county, Minnesota. 
WHILRAYV ESTAVSUBCARENATA': TSSD -cpfeicals asteisitce ass's croton «ocala nie oi aanein gtde « -Aesmieee 
The right side and an antero-dorsal view of a cast of the interior, showing the 
form of the shell and obscure traces of radiating stri# on the posterior part. 
Middle Galena, Goodhue county, Minnesota. 
WHITEAVESIA MODIOLIFORMIS Meek and Worthen............2 ..eecceeceecccecs 
The left side of an internal cast, Beloit, Wisconsin. Survey Mus. Reg. No. 8341. 
View of the original type of the species. In the drawing the base and the ante- 
rior end is restored and the right valve tilted, so as to give an exact dorsal 
profile. ‘“‘Lower Blue” beds of the Trenton formation, Mineral Point, Wis- 
consin. Illinois State Museum. 
COLROMYA "DEMISSA, "T. AD resist facts stclorsreyole’(e lores a'o.s,s:atarw sis eles eels ouictoln sig ele aa seee erat 
The nearly perfect shell upon which this species is founded; of the natural size 
and x45. Middle third of the Trenton shales, Chatfield, Minnesota. 
ORTHODESMA SUBNASUTUM Meek and Worthen ............ccccseccccereccceccess 
Lateral and dorsal views of an entire cast of this species. Galena limestone, 
Dixon, Llinois. 
OR THODESMASSCHUCH MREt I SD torso sjotate cosines cata ees o1cnte clei du hes wat eeteels 
Lateral and dorsal views of a cast of the interior, which is imperfect posteriorly, 
but in good condition otherwise. Middle Galena, Fillmore county, Minnesota. 
Survey Museum Reg. No. 8343. 
FS MRNAS PICA AS FL AND SOY) moors mete tee ste ate 70 bela wlniare' #7574 n,n ja,0 Se sara ot aoeie Rise aE aisle ee 
Interior of the left sai z as obtained ina gutta- percha impression of a cast of 
the interior. 
Hinge and anterior muscular scar of the left valve, 
eters. 
magnified nearly two diam- 
Trenton limestone, Minneapolis, Minnesota. 
UAT ETOAC ET COSA- WITICH: ox acwicianrs vice nae'en cic ceiclaninie talent - 20a See crelenin/enoeraenaatare 
Views of the exterior and interior of a large right valve. Upper part of the 
middle third of the Trenton shales, Goodhue county, Minnesota. 
LOVER. 
511 
516 
515 
518 
563 
