696 SCHUCHERT AND TWENHOFEL ORDOVICIC-SILURIC SECTION 



more than 2 feet in thickness, which prove the shallowness of the sea 

 during their deposition. 



The strata of this division are seen to best advantage at the west end, on 

 the north side of Anticosti, about English Head and Macastey Bay. To 

 the east of the last named place the lower portion of the capes is formed 

 by the higher beds of Ag and the "track bed" or A^, the latter dipping 

 below sea-level at the base of Observation Cliff. Beyond this point no 

 strata of A occur, all the exposures belonging to higher divisions. On 

 the south side of the island Division A is not above sea-level. 



The zones of the English Head formation are as follows : 

 Early Richmondian heds. P^^^ 



Ai. Seen on the reefs about English Head. Thickness 44 



A2. The lower part of English Head 25 



A3. The more fossiliferous lower portion of English Head 10 



Dinobolus deds. 



A4. The main or upper beds making English Head 63 



In the lower portion are zones of Dinodolus in the greatest 



profusion. 

 A5. Seen to best advantage between English Head and about Macastey 



Mountain, where portions of the higher beds of A4 may also be 



seen 86 



Ae. The "track bed," with the impressions known as 8cBrichnites 



ahruptus, and seen at numerous places from English Bay to 



Observation Cliff, 6 inches. 



The fauna is a large one and practically the same throughout this 

 division. The more diagnostic forms listed below are in the main de- 

 rived from A4 and A5 : Streptelasnia rusticum, Favosites (?) prolificus 

 (attains to 2 feet and more in diameter), Calapcecia antic ostiensis, Glima- 

 cograptus putillus, Dinoholus, n. sp. (A^)^ Hebertella maria, Dinorthis 

 porcata, Dalmanella meeki, Strophomena fiuctuosa, 8. hecuha, Leptcena 

 nitens (close to L. unicostata), BJiynchotrema anticostiensis, R. perla- 

 mellosa (but a single specimen from lower Ag), Catazyga anticostiensis, 

 Pterinea prolifica, Conradella pannosa, Liospira americana, Pterotheca cf . 

 transversa, Ascoceras ? large n. sp., Actinoceras anticostiense , Camero- 

 ceras, Ceraurus pleurexanthemus. 



Correlation. — A hasty examination of the fossils of this division may 

 give the impression that their age is that of the Black Eiver or lower 

 Mohawkian, but after further study it is seen that many species are 

 present which elsewhere are known only in the Richmondian. These 

 diagnostic fossils are found more especially to the west of the Cincinnati 

 axis, as at Wilmington, Illinois, and Spring Valley, Minnesota. Such 

 are Streptelasma rusticum, Climacograptus putillus, Dalmanella meelci, 



