Vili ILLUSTRATIONS. 
Page. 
PEATE) Xi. Rhizostomitesadmirand@usses ees esse eee sees eee ee eee eee eee ee eee eee 184 
XLT. Rhizostomites lithooraphicns sess seen eae aaa Heese eee ae eee eee eee 186 
XLII. Rhizostomites lithographicus; R. admirandus; Medusina staurophora. .-.----.---- 188 
XLITI.. Hexarhizites insignis:.c22 << ease ct sae nec sede eee SRE eee oe eee ee 190 
XLIV. Medusina deperdita; Acraspedites antiquus; Medusina porpitina.........--..----- 192 
XLV. Medusina quadrata; M. bicincta; EKulithota fasciculata ....-....-...--.-..--.--.-. 194 
XLVI. Mednsichnites...o2 jae eco sees sesso eyo see eye ee a ee eee ee eee ees 196 
XLVII.: Discophyllumipeltatunn 5.220 -- ees | eo see ee ee REE eee ee ee eee eee eee 198 
Fig. 1. Brooksella alternata; diagrammatic central yertical seetion........-.-.-------------- 9 
2. Archirhiza primordialis; subumbrella view.----------------5------- e+ --=225--55 oe" 10 
3. Cannorhizarconne xa 12d cra ese Ch Omer emma a eee eee 11 
4. Brooksella alternata; diagrammatic central vertical section through the umbrella lobes 
(Samoe/as figeil) Soe ss Sec Secon sess es Se eee Cee See reer eae ee ae re eee 28 
5. Brooksella alternata; diagrammatic central vertical section through the central axis 
between) the radiatinevobest2s.. ..5 220 eee sean eee eae See eee ea eee eee 29 
6. Brooksella alternata; diagrammatic vertical section through the central axis of fig. 
Sof Pl. Vasc ses os sted eeteis doe Ga ed cede eae ns es ee Seg elas eo eee ate 29 
7. Brooksella alternata; diagrammatic vertical median section of same specimen as fig. 6. 29 
8. Laotira cambria; diagrammatic vertical section of the specimen represented by fig. da 
Of PLXY MW 2 ccc. cok ieee c cee assem eee ween See ee Sole ee Bene eee eee eee 34 
9. Laotira cambria; transverse section of a complex specimen.....-.--.---.------------- 34 
10. Laotira cambria; diagrammatic transverse section of a complex form .......--.------ 35 
11. Laotira cambria; hypothetical canal system of the exumbrella of fig. 1 of Pl. XIV_--- 36 
12. Laotira cambria; restoration of the canal system of the subumbrella lobes of the 
specimen illustratedibyatic dof ISexLl sas cee ee- oes eee ee ee eee ee eee 37 
13. Laotiva cambria; theoretical diagram of the canal system of the exumbrella and sub- 
MUM VLE] LO WES oh ei or 2) Ody kad ANC Was ee eee ae ee 37 
If. ‘By thotrephisi(?)asterotdes.cs stan. sccm see cee See ee ee ene es cee 42 
15. Dactyloidites asteroides from Parker's quarry, Georgia, Vermont. .--...---------.----- 46 
16. Medusinawadinta 22.2 cee esd sae ee ee eet = Hee See ane ee ee Seine eee ess eee reee 58 
17. Semieostomites: zittelis = ss -c5-2- eeee asic eee SePEe ee ene eae tee eee eee 71 
18) “Rhizostomibes) =< 22c.c mem ee eae ee Se = eee eee ease eee at eee ene =e ee eee 80 
19 Rhizostomites t= rma a= fee se eee ee eee eres eee eee eee 81 
20, Hexarhizites/insignis(==5- 25-6 2-6 e-o- eee eae ne one ese nee S es a eee eee 87 
ail, Leptobrachites trig onoprachits) esses see eee eee eee ee eee see ee ee 89 
22. eptobrachites=tri yonobrachius,oeae. ce saseeees aes oe eee ee eee ee ee 90 
23.- Medusina deperdlita::..... 22 22 dcenrsc2k tow ooo tere are Ss a ae ee 92 
24. Medusinaaitaviarsis so2a-c6 csceie= se cts See aetissae os eee ee eect Sees cee ae eee eae eee ee 96 
25. Medusitesi(?y latilobatus: 2: -1--ccsene = ecm concer eee Se ee ee 99 
26. Enlarged section of a portion of Medusites (?) latilobatus -........-..-..--..--------- 100 
