I'LATK XI. IV 



All i lie Bgurtwon ihU plaUr re mMulSwi about twenty dlanMltn. . 



I. Kri:v< IIII.INA Hrin n.\T.\ I'lrlch. 



: f,-<-t left valv.- <.f thin species. Lower thlnl t the Trenton shale*. Fillmorw 

 county, Minnesota. 



\ UKIK TI.ATA, var v,n. var 



n. th<- upper third of the Trenton shales at St. Paul, MlnneoU. 



Fig*. 3and]4. KVBYCHILINA SUBRADIATA Ulrlch 



:i Interior of a perfect right valve. 



4. Nearly perfiTt Ml ralre, showing the usual characters of the species at It occurs 



In Minnesota. 

 4o. Section of same across central portion of valve. 



Lower third of the Trenton shales, Minneapolis, Minn. 



figs. 6 to 7. EvKYuiii.iNA(t)STincrnucA, n. sp... 



<B*e tlco plau XLV, (.. 4-tt.) 

 :>. Interior of a right valve. 



6 and 7. Exterior and anterior views of a more elongate left (?) valve, 

 Upp. r third ..f the Trentob shales, St. Paul, Minn. 



FlgS. 8 U) 11. CTENOHOLIHNA rCLCRATA, n. Sp B "* 



9 and 0. Lateral and posterior views of a left valve, presenting the usual characters of 



the species. 

 10 and II. Lateral and dorsal views of a right valve, resembling In certain respects the next 



-I*-.-,. - 



r pper third of the Trenton shales, St. Paul. Minnesota. 



Figs. 12 to 16. CTENOHOLHIX A CKASSA Ulrlch 



12 t-i 14. Lateral, posterior, and dorsal views of a left valve. This Is the original type 



of the species. Upper third of the Trenton shales, St Paul, Minnesota. 

 15 to 16. Lateral and posterior views of another left valve from the same locality, differ- 



Ink* In several respects from the type. 



FlgS. 17 to 19. JOHEOtLLA OMCURA, n. sp 



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. 



Figs. 20 to 22. DREPANELLA BIOENERIS, n. sp - 



20 and 21. Side and posterior views of a left valve. Lower Trenton limestone, Minneapolis, 



Minnesota. 

 22. Longitudinal sectional view across the central part of the same. 



K . 23. DlCRANKLLA SPUfOHA, n. Sp **S 



(8*e aUo plate * LVI. fig. 41. ) 



A left valve of this species. Middle third of the Trenton shales, Minneapolis, 



Minnesota. 

 Figs. 24 and 25. DICRASELLA (?) SIMPLEX, n.sp 696 



(8e Uo plate ZLTI, fl*. 41.) 



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. 

 I.. 26. DICRAMELLA BicoRNis, n. gen. et sp 665 



<8*e aUo plate XLVI. fifv t and 40.) 



A right valve wanting only the posterior part of the marginal frill. Middle 

 third of the Trenton shales, Minneapolis, Minnesota. 



Figs. 27 and 28. DICRANELLA MAKWNATA, n. sp 666 



Lateral and posterior views of a right valve. Trenton shales, near Fountain, 

 Minnesota. 



Figs. 29 to 35. BTTHOcrrRis CYLINDRICA Hall, sp 



29 to 31. The left side, dorsal, and posterior views of an average example of this species. 



Lower beds of the Cincinnati group, Cincinnati, Ohio. 

 33. Yi.'w <>f the Interior of a right valve, showing a slight central thickening of ' 



test. From the same locality. 



33. Yi-ntral view of a complete carapace: also from Cincinnati, Ol. 



34 and 35. Lateral and dorsal views of a small right valve, which Is also a little narrower 

 than u-ii:il. Galena shales. Cannon Falls, Minn. [ora. 



