Fig. 
Figs. 
Figs. 
sand 4, 
DibOwaai 
De 
- 6and 7, 
Figs. 
Fig. 
Figs, 
Fig. 
Figs. 
Figs. 
8 to 11. 
Sand 9. 
10 and 11. 
- 12 to 16. 
12 to 14. 
15 to 16. 
17 to. 19. 
20 to 22. 
20 and 21, 
22. 
23. 
24 and 25. 
27 and 28, 
29 to 35. 
29 to 31. 
32. 
33. 
34 and 35. 
PLATE XLIV. 
All the figures on this plate are magnified about twenty diameters. 
UR CHIEN AG RUE TIOU MAMA WITCH! Petras okie eeelaste dere malelalleeaaais catvleiees siee« 
A perfect left valve of this species. Lower third of the Trenton shaies, Fillmore 
county, Minnesota, 
HURYCHILINA RETICULATA, Var. INCURVA, Di VAL... cece. cece scdsecderecnsccssceces 
Left valve from the upper third of the Trenton shales at St. Paul, Minnesota. 
HURRY, OUT LINVAG, SUS AND) IAC Avee UD let @ LD reeeveyaney tet crete atenevel stclerahe ers fefeyii eller stele /siavereteierePareisets¥asic si 
Interior of a perfect right valve. 
Nearly perfect left valve, showing the usual characters of the species as it occurs 
in Minnesota. 
Section of same across central portion of valve. 
Lower third of the Trenton shales, Minneapolis, Minn. 
HU RY CHNEINIAC(?) SYMMEDRIC A MeaSPeyesicisaleauraleb/stensteretees ay sslsf-lolu srs iricioiejaicie eile sree eins 
(See also plate XLV, figs. 4—6.) 
Interior of a right valve. 
Exterior and anterior views of a more elongate left (?) valve. 
Upper third of the Trenton shales, St. Paul, Minn. 
CRENOBOLBINA HULCRAT Alin Speliee. crease aero nisclede aint olsta atrrais minis aie oiaron tel siete 
Lateral and posterior views of a left valve, presenting the usual characters of 
the species. 
Lateral and dorsal views of a right valve, resembling in certain respects the next 
species. 
Upper third of the Trenton shales, St. Paul, Minnesota. 
CTENOBOEBINAG CRASS Ads Uli Chie vetrm actrees eiere wet barsCare rately asta sratictiorsloreeret arate) as 
Lateral, posterior, and dorsal views ofa left valve. This is the original type 
of the species. Upper third of the Trenton shales, St Paul, Minnesota. 
Lateral and posterior views of another left valve from the same locality, differ- 
ing in several respects from the type. 
JONESHMGEAROBS CUI AY wills: SPs araterate| irs lel iesevsaec toners) sic tenet cictolare cas reatielalaliateien semmageisiciciteess 
Left and right valves and an interior view of the first. The ‘‘horseshoe” ridge 
is very obscure in its lower curved part. Galena shales, Cannon Falls, Minn. 
DRE ANE Avs BIGHNEURIS, “1, SDAlcc..tsias crc seine cele scsiesietseisie es oereerde ne wads clo nae evecare hs 
Side and posterior views ofa left valve. Lower Trenton limestone, Minneapolis, 
Minnesota. 
Longitudinal sectional view across the central part of the same. 
DI CHAN E TDAGSEUN OBAGI iS Day ltcicts civ-cs).vi dei rane aoiera coe sal ate wserieie ier ata eater ee 
(See also plate xLvI, fig. 41.) 
A left valve of this species. Middle third of the Trenton shales, Minneapolis, 
Minnesota. , 
DICTA HET AY (9): SUMP IHX, SUAS]: ae tiaras eerie erage terapel teva oleta leis ols cksicle's are sieisiareioiclevecai ate 
(See also plate x Lvt, fig, 42.) 
- Lateral and posterior views of a left valve. Galena shales, Cannon Falls, Minn. 
In fig. 24 the oblique spine on the left side of the center appears scarcely 
prominent enough. 
DICHANERMAGBICORNIS ttn OS eMMehiSpiaatscraeoerdeecerise eta elaaicnicioneieceie eine 
(See also plate xLv1, figs. 39 and 40,) : 
A right valve wanting only the posterior part of the marginal frill. Middle 
_ third of the Trenton shales, Minneapolis, Minnesota. 
IDI G USAID MUNSON, TG SOS co anc Coded nade np oocpue soe Moo coodoouons RAHaObOn ace 
Lateral and posterior views of a right valve. Trenton shales, hear Fountain, 
Minnesota. 
BY THO CYP RISE ONVGENDRICAt Etally Sp esetmeteerctamcckrrricrineci ec cine 
The left side, dorsal, and posterior views of an average example of this species. 
Lower beds of the Cincinnati group, Cincinnati, Ohio. 
View of the interior of a right valve, showing a slight central thickening of the 
test. From the same locality. 
Ventral view of a complete carapace; also from Cincinnati, Ohio. 
Lateral ana dorsal views of a small right valve, which is also a little narrower 
than usual. Galena shales, Cannon Falls, Minn. [OVER. 
663 
674 
668 
672 
665 
666 
665 
666 
