1 to 
4. 
BD; 
6 to 8. 
9 to 11 
Figs. 12 to 14. 
Figs. 15 and 16. 
Figs. 17 and 18. 
Figs. 19 to 22. 
19 and 20. 
21. 
22, 
Figs. 23 to 25. 
Figs. 26 to 29. 
26 and 27. 
28. 
29. 
Figs. 30 to 34, 
Figs. 35 to 38. 
35. 
36 and 38. 
37. 
Figs. 39 and 40, 
Fig. 41. 
Fig. 42, 
Figs. 48 to 46. 
43 to 45. 
46. 
PLATE XLVI. 
All the figures on this plate are magnified about twenty diameters. 
TETRADELLA QUADRILIRATA Hall and Whitfield, sp...................200. sees 
Posterior, side, and dorsal views of aright valve. Middle third of the Trenton 
shales, Minneapolis, Minn. : 
Another right valve. Birdseye limestone, High Bridge, Kentucky. 
Inner side of a right valve. Minneapolis. - 
Three views of a left valve, differing from the usual form in n unimportant partic- 
ulars. Minneapolis. 
Three views of a variety, agreeing with var. simplex in wanting the posterior 
marginal loculi. Trenton shales, Fountain, Minnesota. 
TETRADELLA LUNATIFERA Ulrich............ ORS TonGAnD OSSD Arce Cece mora bon ator 
Three views of a left valve of a variety of this species. In other specimens that 
were found with this one the antero-median ridge is more distinctly double. 
(See cut, p. 680.) Galena shales, Cannon Falls, Minnesota. 
EDO IAN GUD ATRES, AGS Ps eve cis alele telepoersteteles shetneloustae masters laieeyaicyemtcietepap=teehetale restate eer ee 
(See also plate XLitlI, fig. 89) e 
Two views of a weather-worn valve, apparently of this species. Trenton shales, 
Fountain, Minnesota. 
WKS OVA (PA) Ga ojo O-OA 06S) Nya desagnbaacorusoahouden coe Hbors Sor aonb Osan eadognadd 
Side and sectional views of the remarkable valve upon which this species is 
founded. Trenton shales, Fountain, Minnesota. 
CERATOPSISIGHAMBE RSD OMIUIGT posers isistaeteetetclete etere tater ieteiaie te leletareta 0) ofeleisleitisin/ajereretatalaeets 
Side and ventral views of a left valve of the usual form. Upper third of the 
Trenton shales, St. Paul, Minnesota. 
Inner side of a more elongate right valve, from the same locality. 
Another right valve from the same locality, peculiar in having the small post- 
median ridge divided. 
IBOLDIAC RUIN GUL OLD EAS Mat SPs.!esejsiale erete stove ave ebeisichstoseyoferateferetoit tales fete Palen ialareeteineremes lar 
Three views of aleft (?) valve. Galena shales, Cannon Falls, Minnesota. 
BOLTLTACSUB ALO WADA ily SD Ne tate aieteaietotoielore clecia evenelelcleveletey etclelatenaverete la ahelepeleleaketedsinelaie valet rs 
End and side views of a valve of this species. Trenton shales, Fountain, Minn. 
A small valve from the same locality. 
Large and relatively high valve from the same position at Cannon Falls, Minn. 
DILOBELLA TYPA, D. Gen. Cb SP...- 6s eee cece cece cate n eee s ccc tens ce sees ree eteeseres 
Figures of three valves showing slight variations. Upper third of the Trenton 
shales, St. Paul, Minnesota. 
DREPANELTA: BIA THR AMATS, sai Parietal orale sie eelovevercieie rs eae ieieloetel ore ofatet= eteiaiat inetatete 
A right (?) valve of the usual size and appearance. 
Ventral and posterior views of a left valve. 
Interior of a right valve. 
Upper third of the Trenton shales, St. Paul, Minnesota. 
DICRANELL A BICORNIS, UW. }ZED~) Cb. Spee syeraye aie=\ oe oicrelela a} elu sivie (allem sl=/slol.e cjalvle)sieisi= alv/elelere 
(See also plate xiv, fig. 26.) 
Side and posterior views of a nearly complete right valve. Middle third of the 
Trenton shales, Minneapolis, Minn. 
DICHANE DE AVS PINOS A, is SD isiere wiairetelolatay aim o/s claloialeistofey ele tnlate tale iatelalelemuieetela dieiaistare aval teteke 
(See also plate xLtIy, fig. 23.) 
Posterior view of a left valve. 
DICRANE ETA?) (SLIM PIFERS “POS, a> wie tietals ‘ercie of stale ovelele oni \najeresalu’si= olalols)siafejetalnissiel<aimistaliale 
Ventral view of the valve figured on plate XLIV, figs. 24 and 25, 
ERAS ETT AY ATBIO SAY GOEYS DD nzesay ciers eke scctoue Fare cl sieial erate phe egstarenste sitters lod elereia otckeleaketetate jetetaisye 
Anterior, dorsal, and left side views of an entire carapace. Galena shales near 
Cannon Falls, Minnesota. 
Somewhat weathered and relatively longer left valve: from the same locality. 
680 
682 
683 
676 
669 
669 
673 
671 
665 
665 
666 
656 
