PLATE IV. 
Rigs sLibo rps. PHYEEOPORINATS UB LAUXCAN WNL IUD ere serrate asi sianielcleratetncia steisserefarateveystarstelorclalarsietevale sisters eieietsie terete 209 
land 2. Reverse side of small fragment, natural size and portion of same x9, showing 
striated character of this side in young or exfoliated examples. Lower Trenton lime- 
stone, Minneapolis, Minn. Survey Museum. Reg. No. 5954. 
38and 4. Another fragment from the same locality, exposing the obverse side, natural size, 
and portion of same *9. 
5. Tangential section, 18, showing appearance of zocecia at varying depths. 
6. Two transverse sections of branches, <18. 
7. A rather loosely woven frond from the ‘‘Glade” limestone at Lavergne, Tenn.; natural size. 
Migs: 8itod4. Ver yvAGLOPORUGA RW DICT GATAS (EDAD) i acres reve cp tnersisleleletatereis kale alevetstcreraeseieteteielrele nies elalereeearetse 210 
8. A frond exposing the reverse side, natural size, Minneapolis, Minn. . 
9. Portion of same, <9. 
10 and 11. Another fragment from the same locality, natural size and x9. 
12. Small fragment, likewise from Minneapolis, exposing the obverse face, *18. 
13 and 14. Obverse and reverse sides of two fragments obtained from washings of Galena 
shale at Cannon Falls, Minn.; <18. 
15. Tangential section, *18, of an example from Trenton Falls, N. Y. 
Hi gS> 16) bor eee evar FOP ORTNIAGEDAU TE MU reper taretorafelarctelafeoctstotshotetolatststatelstanletelatetateletoteetstarstet state cteteteter-ietai senate 211 
16, Reverse side of aspecimen, natural size, showing irregular arrangement of fenestrules. 
17. Celluliferous side of another fragment, natural size, showing the irregular solid swellings. 
18. Surface of same, <9. 
19. Reverse side of same, *9. 
20. Tangential section, <18, cutting the zocecia just beneath their mouths. 
21. Another portion of same section, 18, where it divides the zoarium at a deeper level. 
Upper third of the Trenton shales at St. Paul, Minn. 
