DETAILS OF STRATIGRAPHY 359 



Camarotoechia ? festinata Savage Diaphoro stoma niagarensis var. im- 

 Dalrnanella modest a Savage matura Savage 



Homceospira immatura Savage Modiolopsis concinna Savage 



Leptcena rhomboidalis (Wilckens) Pterinea formosa Savage 



Lingulops ovata Savage Acidaspis halli Shumard 



Protozeuga sulcocarmata Savage 22 Calymene dubia Savage 



Rafinesquina fmesicosta (Shumard) Cyphaspis Girardeaaensis Shumard 



Rafinesquina ? delicatula Savage Encrinurus deltoideus Shumard 



Rhynchotrema f Illinois ensis Sav age Proetus princeps Savage 



The decided Silurian aspect of the fauna of the Girardeau limestone 

 appears in the list presented above. The post-Kichmond age of the 

 Girardeau limestone is shown by the fact that not a single characteristic 

 Eichmond species has been found in the formation, and also by the pres- 

 ence of such Silurian genera as Schuchertella, Homceospira, Camarotoe- 

 chia ( ?), Diaphorostoma, Protozeuga, and Proetus. The only species in 

 the Girardeau fauna that are listed by Cummings from the Eichmond 

 strata of Indiana, or that are known to occur in the Maquoketa (Eich- 

 mond) strata of Iowa and Illinois, are Leptcena rhomboidalis and Cornu- 

 lites tenuistriata, neither of which possesses any stratigraphic significance. 

 • It should be noted also that the most abundant and characteristic of 

 tne Girardeau species, as Schuchertella missouriensis, Rafinesquina ? 

 mesicosta, and Protozeuga sulcocarinata, continue upward into the suc- 

 ceeding Edgewood limestone. Eegardless of whether the Eichmond shall 

 eventually be transferred from its present position in the Ordovician 

 (where in the mind of the writer it should remain) to the Silurian sys- 

 tem, the Girardeau limestone appears positively of post-Eichmond age 

 and clearly represents the earliest deposits of the early Silurian Sea that 

 advanced into this region from the south, the epoch of submergence cul- 

 minating in the Brassfield transgression. 



THE EDGEWOOD LIMESTONE 



Occurrence and stratigraphic relations. — The name Edgewood lime- 

 stone was proposed in 1909 23 for the strata occurring between the Girar- 

 deau limestone and the Sexton Creek (= Brassfield) limestone in south- 

 west Illinois and eastern Missouri. 



In 1898, C. E. Keyes 24 proposed the name Noix oolite for the white 

 oolite bed outcropping along Noix Creek at Louisiana, Missouri, and the 



22 Protozeuga has been defined in manuscript by Dr. W. II. Twenhofel for an early 

 Silurian genus of brachiopods having the general characteristics of Waldheimia, but 

 with punctate shells. 



8 T. E. Savage: Amer. Jour. Sci., vol. xxviii, December, 1909, p. f>17. 



24 C. It. Keyes: Proc. Iowa Acad. Sci., vol. iv, p. 27. 



