302 G.'S. Hume — Stratigraphy and Geological Relations 



Some of the more important fossils are as follows : Re- 

 ceptaculites oiveni, Streptelasma corniculum, S. angula- 

 tum, Columnaria alveolata, C. (PalcEophyllum) stokesi, 

 Halysites quebecensis, Plasmopora lambii, Pleurocystites 

 squamosus , Dalmanella testudinaria, Platystrophia tren- 

 tonensis, Rhynchotrema increbescens laticostatum, R. 

 minnesotense, R. inequivalve, Strophomena emaciata, S. 

 incur vat a, 8. trentonensis, 8. trilobita, Fusispira cf. an- 

 gusta, F. convexa, F. nobilis, Hormotoma gracilis, H. 

 trentonensis, Liospira angustata, L. progne, Lophospira 

 cf. elevata, Maclurina cuneata, M. manitobensis, Maclur- 

 ites crassus, M. crassus macer, Trochonema umbilicatum , 

 Narthecoceras crassisiphonatum, Ooceras cordatum, Or- 

 thoceras amplicameratum, Vaginoceras multitubulatum , 

 Bumastus trentonensis, Ceraurus dentatus, Isotelus 

 gigas. 



Of these, the corals are particularly common in the 

 npper shales, and this level is suitably called the Strep- 

 telasma corniculum zone. The upper limestone is more 

 especially characterized by large gastropods of the Mac- 

 lurea type, after which the zone has been named. 



The fauna shows close resemblances to that of the Nel- 

 son River limestone of Hudson bay (Savage and Van 

 Tuyl 1919), and equivalent strata of Trenton age occur at 

 Frobisher bay, Baffin land (Schuchert 1910), in Manitoba 

 (Dowling 1898), and in Wisconsin, Minnesota, and Iowa. 

 Several fossils suggesting a similar faunal association 

 have also been reported from the Port Clarence limestone 

 of Alaska (Kindle 1911). This fauna, then, belongs to a 

 widespread transgression of the sea from the Arctic in 

 Trenton time. Towards the base of the upper limestone 

 member, or Maclurea zone, there is a fossil crinoid and 

 cystid horizon having Pleurocystites squamosus. This 

 fossil occurs in the Hull limestone of the Trenton of the 

 Ottawa region, and it appears probable that its strati- 

 graphic height is about the equivalent of the Kirkfield 

 crinoid horizon of southern Ontario. 



Upper Ordovician: Richmond. — No Richmond outcrops 

 in this area, although it would be expected to occur from 

 the known widespread marine transgression of this time. 

 Between the top of the Haileybury formation and the low- 

 est known Silurian, there is a stratigraphic interval cal- 

 culated to be about 40 feet. This undetermined interval 

 may possibly contain Richmond strata, but as it is com- 



