98 ROYAL SOCIETY OF CANADA 
CoNJECTURAL LINES OF DESCENT OF THE CANADIAN OBOLI, WITH REFERENCES 
TO THE OLDEST KNOWN ATREMATA. THE ZONAL HORIZONS OF THE 
SEVERAL SPECIES ARE SHOWN IN THE MARGIN. 





Dictyonema Obolus (Monobolina) 
Obolus ( Euobolus) refulgens 
Apollonis aA 
\ / 
he 7. 
Peltura O (Westonia) Iphidea \ DS 
Ella pannula Lingulella Linguella 
| Davisii concinna 
| \ 
| | \ 
NS . 
Olenus | | q L. levis 
| | N 
| \ 
| | hs 
Upper | | \ 
Paradoxides Obolus, sp. | Lingulepis L. radula 
Starri 
Lower | | L. Dawsoni 
Paradoxides | | 
| 
| 
Protolenus Obolus O. (Botsfordia) L. Martinensis 
pristinus pulcher 
| 
| 
| 
O. (Palæobolus) 
Upper Bretonensis 
Etcheminian | O. (P) lens 
|| O. (P) lens-primus 
| 
{ O. (Eoobolus) L. longinervis Lingulalla 
Lower æquiputeis Selwyni 
Etcheminian | O. (E) discus is i 
O (E) triparilis| L. Gregwa if L. longovalis 
/ 
/ 
7 
/ 
Coldbrook O (E?)torrentis} L. pumila L, cf. longovalis 
Base of the 
Cambrian Leptobolus Obolus Lingulepis Lingulella 




| pl | 
Atremata 


Pre-Cambrian 

