ART. 14 MICHIGAN TRAVERSE GROUP — POHL. 31 



Fistulipora vesciculata (Hall and Simpson). 



Botryllopora cf. socia-lis (Nicholson). 



MoTWtrypella ohioensis Stewart. 



Reteporina striata (Hall). 



Stre'blotrypa cf. hamiltonensis (Nicholson). 



Stropheodonta cf. demissa (Conrad). 



LeptostropMa cf. perplana (Conrad). 



Pholidostrophia species cf. iotvensis (Owen). 



Chotietes near coronatus (Conrad). 



Chonetes fragiUs Stewart. 



Leiorhynchus lu'cas*i Stewart. 



Atrypa reticularis (Linnaeus). 



Spirifer near oweni Hall {euryteines Owen of Stewart). 



8. prolificum Stewart. 



Grammysia species cf. rvodocostata Hall. 



Pterinea near flahella (Conrad) and several varieties. 



Phacops milleri Stewart. 



The lowest Traverse is thus seen to rest on Onondaga strata and 

 is nowhere known to overlap on younger beds. The basal Traverse 

 is therefore immediately post-Onondaga in age. The basal contact 

 may again be seen in the Alpena region, but since the exact relation- 

 ships of the Dundee and the overlying " Manitoba beds " are not 

 completely understood direct inferences are best not drawn there. 



The Traverse beds thicken to the northward until at their northern 

 edge of outcrop in the northern counties of the Southern Peninsula 

 of Michigan they aggregate between 500 and 700 feet of deposits, 

 mostly highly calcareous. The upper beds of the Thunder Bay stage 

 on the east carry an abundant and very distinctive association of 

 species already cited in part on a preceding page. 



Turning now to the Middle Devonian of southwest Ontario a few 

 sections are found exposed on and near the shores of Lake Huron and 

 on the Ausable River and a few of its tributaries in Ontario. These 

 are the famous Canada West localities which have been for a century 

 a paradise of paleontological collectors. Much has been written on 

 the faunas and stratigraphy of the district, and the occurrence has 

 played an important part in former conceptions of Devonian paleo- 

 geography, but the full significance of the sections has only recently 

 been learned. Mr. Charles Southworth, of Thedford, an ardent 

 local collector, discovered in 1926 beds representing the lowest exposed 

 portion of the mid-Devonian sequence of the district. These may 

 be seen at times of low-water level in the bed of the Ausable River at 

 Grand Bend on the line between Lambton and Huron Counties. The 

 sequence is carried upward interruptedly to the southward through 

 the " Ipperwash limestone " and the " Olentangy shale," which under- 

 lies the " Encrinal limestone " of this section. The exposed succession 

 to the base of the " Encrinal limestone " aggregates close to 60 feet of 

 beds and according to the fossil content is directly correlatable with 



