700 SCHUCHERT AND TWENHOFEL— ORDOVICIC-SILURIC SECTION 



A and B when contrasted with the Ohio Eichmondian is the almost total 

 absence in the former region of the Trepostomata bryozoa. The Atlantic 

 waters of this time seem to have had no great development of these ani- 

 mals, for the same condition also occurs in Europe. In the Ohio region 

 of the Mississippian sea these bryozoans are in wonderful abundance. 

 To the west of the Cincinnati axis they are also scarce, but here they are 

 more often seen than on Anticosti. 



In the Ohio region Beatricea ranges from the base of the Liberty to 

 the top of the Elkhorn, a thickness of probably less than 100 feet, but on 

 Anticosti these fossils range through 702 feet of limestones. Here the 

 forms of life generally endured a long time, and the Gulf of Saint Law- 

 rence may be regarded as on the continental shelf in close proximity to 

 the permanent Atlantic (Poseidon) Ocean^ where the physical conditions 

 were more equable than in the Mississippian continental sea. Another 

 striking case is the brachiopod Gatazyga headi, that in the Ohio region is 

 restricted to a very limited zone, usually one of a few inches, while on 

 Anticosti C. anticostiensis ranges through all of A and the lower third 

 of B, or through 320 feet (south shore) to 430 feet (north shore) of lime- 

 stones and shales. Dinorthis porcata occurs for the first time in the Eng- 

 lish Head stage A^-A-, and reappears again at the base of the Ellis Bay 

 formation. 



At Stony Mountain, Manitoba, occurs a Eichmondian fauna that is 

 more clearly related to zone Bg than to the higher beds. Whiteaves^® has 

 listed 55 species from this western locality, and of these the following 

 also occur on Anticosti: Streptelasma rusticum, Favosites ( ?) prolificus, 

 Protarcea vetusta, Beatricea undulata, B. nodulosa, Sceptropora facula, 

 Strophomena neglecta, S. fluctuosa, Rafinesquina ceres, Leptcena nitens, 

 Dinorthis porcata (the writers have seen this species from Stony Moun- 

 tain), Rhynchotrema perlamellosa, R. anticostiensis^ and Cheirurus 

 icarus. When the Anticosti fauna is completely known there will cer- 

 tainly be other common species added to the above list. 



The Charleton formation is not seen again to the west of Anticosti for 

 375 miles, when it reappears at Lake Saint John, at the head of the 

 Saguenay. Here Billings reports Catazyga headi and Beatricea. The 

 next occurrence is at Three Elvers, to the west of Quebec City, more than 

 500 miles west of Anticosti. C. headi also occurs at that locality. 



GINOINNATIC SYSTEM. GAMACHIAN SERIES 



General discussion of the series. — The Gamachian series, also of the 

 Cincinnatic system, follows the Eichmondian series and has no known 



16 whiteaves : Geological Survey of Canada. Pala?ozoic Fossils, vol. iii. Pt. II, 1895, 

 pp. 111-128. 



