led byeVAM ey) OST 
Migs 1 to\3, 6, and 8)todl-, (ISTIGCTOPORETE A ANGUIEARIS UII soe: cteleletnlele aleirielete/olatel=\-1mtatalel=ln eleleia!elen =reieleisie 182 
1 to 3. Three specimens of the usual form of this species, natural size. 
6. Surface of an average example, <9. 
8,10 and 11. Tangential, transverse, and vertical sections, X18, prepared from the oldest 
example at hand. 
9. Small portion of a tangential section X50, showing the minutely tubular character of the 
divisional line between adjoining zccecial walls. 
Lower third of the Trenton shales at St. Paul and Minneapolis. 
Figs. 4,5 and 7. STICTOPORELLA ANGULARIS, Var. INTERMEDIA, D. Val.........seesceeeee ee cece cece 183 
4. A small subfrondescent example from the base of the shales at Minneapolis. 
5. A fragment of the usual form of the variety from tne same horizon in Fillmore county. 
7. Surface of same X18, showing the extreme paucity of mesopores and in the upper left 
corner a portion of one of the clusters of thin-walled zocecia. 
Migs 12 L019) Ss STICTOPOR EGET AVM OND TOE ER ACUI © <ijelereilevereiseietcialersrelelelelsi=lelereinistelefersrelats wdoadosoaocaac 183 
12 to 14. Three specimens of this species, natural size. The original of fig. 14 belongs to 
the Survey Museum. It is one of a number bearing the register number 5946. 
15. Surface of original of fig. 12 <9. } 
16. Tangential section of an average specimen, X18. 
17. Small portion of same section <50, to show the structure of the inter-zocecial lines. 
- 18. The basal or prostrate portion of several zocecial tubes as shown in another tangential 
section, X18. 
19. Vertical section, <18. 
Lower third of the Trenton shales at Minneapolis. 
Bigs. 20 and! 21.) {STICTOPOREDL ASRIGID ASIN saceseic cietreerncle seleislereteiceiee elellete ea clelersiisisteta steieioreeesieafetere 180 
20. A fragment of the natural size and the greater part of it <9. 
21. Portion of same, *18. 
Lower part of the upper third of the Trenton shales at Fountain, Minn. 
Figs, 22 and 23. STICTOPORELLA CRIBROSA Ult................- Rsareleialeeatevavoverors aielate Gorstavere (ererniaiarelereTarereretcte 184 
22. Vertical section, x18. : 
23. ‘Transverse section, X18. (See also plate X). 
