I'LATK Xl.lll 



! .. I In Ifur** ara niaflillnl nil. -ii I I . 



ii. sp Kfi 



Aril. -.ii and ventral view* of s left valve. L. 10 lln)et 



M . Minnesota. 



Figs. | to I I.- . M.V I-KK-IM II.IH, n. sp. 837 



'I'M-' rittht slit.', anterior and ventral views of a rath. -r small specimen. Mi 

 iluril i.' ion shales, Minneapolis. Minn. 



Flg. 7 ! '' I.i MACKA, n 



The right side, interior and ventral views of the specimen deKrlbed, showing 

 the re.marknti. ''"MiprwMed character <if the anterior part. Middle third of 

 th<' Tri-iiion shale*, Minneapolis, Minn. 



10 to 14. LKI-KI. TKS Conrart 34 



10. Cut of the Interior >r the larger (right) valve, showing Impression* of the two 

 sets of Internal papilla* along the ventral margin, x 2. Lower Trenton lime- 

 ton*. Minneapolis, Minn. 



11 t'> U. l>"ral. ventral, right side, and posterior views, x 2, of an excellently preserved 



test irapace. from tin aiu<- foroiatlon and locality. The "eye tu- 



lierrle" |s unusually dlstln 



Al'AIti IIIIKs ELL1FTH I'*, ii. sp 644 



: : I '-t.-rlor and v.-ntral views of an entire carapace. Lower third of the Trenton 



hale*, Minn 

 16. The right side of another specimen from the same locality. 



Fig*. 1- to 5). Al'ARi HITKS MINUTIMIMU8. var. TKKNTOMENSIS 64 



A small right valve from the Trenton shalea, near Fountain. MlnnewiU. 

 19 ami -X. Lateral and ventral views of a larger valve from the Galena shales, near Cannon 



Kails, Minnesota. 



Figs. 21 to 25. CYTHKHKI.I.A? KI-OOSA Jones, and var. AROTA, n var 086 



: Lateral and edge views of two valve* of this species, from the Galena shalea, near 

 Cannon Falls, Minn. 



25. A valve of the var. ARCTA. from the middle bedaof the Galenaof GtNtdhue county, 



' Minnesota. The generic position of this opeeies la doubtful, and, to facilitate 

 comparison with 0yfAocy;>ru and allied genera, thin specimen has been drawn 

 with the convex margin uppermost. 



Fig*. 2A to 29. PRIMITIKLLA MJIITLANS. n. p MX 



26. Left valve somewhat doubtfully referred to this species. 



-'7 to 29. Three vlewH of a typical right valve. Both specimens from the Trenton sbale*. 

 near Fountain, Mlnneola. 



Fig*. 30 to 34. MACHOXOTXLLA SOOFIBLDI, n. gen. et sp 084 



30 to 32. Three views of a valve from the lower Trenton limestone at Cannon Falls, Minn. 

 .13 and 34. Two views of a long variety from the Blrdseye limestone at Hitch Hrldgp. ' 

 ntucky. 



Figs, 35and36. AI-AIK nn > AKKBCTUS, n. *p 646 



Two views of a left (?) valve. Upper third of the Trenton shale*, St. Paul. Minn. 



tt and 38. Al'ARCHITK-s CHATKlELDENStS, n. sp. 64 



Two views of a left valve the surface of which Is somewhat abraded. Middle 

 third of tin- Trenton shales. Chat Held, Minnesota. 



Fig*. SB to 41. Si IIMIIITKI.LA I.NCXJMPTA, var. auB^EqcAUB, n. sp. et var 642 



<8M !<> plaM XLT. flc*. n. a and B.I 

 ws of a right valve. Galena shale*, near Cannon Falls, MlnneaoU. 



IIMinTKI.I.A PRA!" !l 640 



42. F.xt.-rior .f a riht valve, x 10, showing the broad border. Lower Trenton 



stone, Mineral Point, Wisconsin 

 43 and 44. Ventral and posterior views of sa ; 



Flgfl. 45 to 47. SCHMIDTBLLA AFFIMH, n. sp 041 



45 and 46. Anterior and side views of a right valve. Galena shales, near Cannon Falls, 



Minnesota. 

 47. Interior of the largest right valve seen. The specimen Is slightly distorted so 



that the hinge In bent inwardly. 



IOTMLJ 



