89 



PoLYTROPis, DeKoninck. 



In a paper on the development of the gastropoda from the Cambrian 

 to the Trias,* Professor E. Koken remarks that, in his view, the genus 

 Oriostoma of Munier Chalmas includes very different things. The typical 

 species of Oriostoma (or Horiostoma, as the word is amended by Fischer) 

 he thinks belong to the Capulidse, while the forms from the Upper Silurian 

 described by Lindstrom (excluding 0. helicinum, 0. dispar and 0. nitidissi- 

 mum) group themselves around the Euomphalus rugosus and E. discors 

 of Sowerby, for which DeKoninck, in 1881, proposed the genus Polytropis. 

 This latter genus is referred to the Turbinidse by Lindstrom on account 

 •of the nacreous structure of its test and the peculiarities of its operculum. 

 According to Koken, Polytropis, as understood by him, extends very far 

 back in time, as it probably includes the " Pleurotomaria (?) Calphurnia " 

 of Billings,! from the Quebec group of Newfoundland, which is, he says, 

 nearly related to " Oriostoma glohosum.'' 



In the " Geology of Canada " (1863, p. 444) Euomphalus rugosus, which 

 would now be called Polytropis discors var. rugosus, is recorded as occur- 

 ing in the Silurian (Upper Silurian) rocks of Port Daniel, in the Baie des 

 Chaleurs, and the Pleurotomaria princessa of Billings, J from the Lower 

 Helderberg rocks between Cape Gasp^ and Cape Rosier is also a Poly- 

 tropis. 



Some of the depressed conical, solid, shelly opercula, with numerous 

 narrow coils, that were formerly referred to Euomphalus by English 

 authors, are now known to belong to species of this genus. Such opercula 

 are not uncommon in the Guelph formation at Elora and Durham, and 

 two of these are represented on Plates 3 and 7 of the first part of this 

 volume. Five species of Polytropis are now known to occur in this 

 formation in Canada, viz., P. sulcatus ( = Gydonema sulcatum, Hall); 

 P. niacrolineatus ( = Euomphalus macrolineatus, Whitfield); P. crenulatus 

 ( = Straparollus crenulatus, Whiteaves) ; and two which were previously 

 undescribed. 



PoLyTROPIS SULCATUS, Hall. (Sp.) 



Plate 13, figs. 9 and 9 a. 



Gydonema sulcata, Hall 1852. Pal. N. York, vol. II., p. 347, pi. 34, figs. 



1, a-d. 



Billings 1863. Geol. Canada, p. 343, figs. 350, a-b. 



Cyclonema svlcatum, Whiteaves... 1884. This volume, pt. I., p. 18, pi. 3, fig. 5. 



*Separat-Abdr. Neuen Jahrb. fur Min. Geol. and Palaaont, 1889, Beilageband VI. 

 tGeological Survey of Canada, Pateozoic Fossils, vol. I., p. 230, figs. 214, a-h. 

 X " " " vol. II., pt. 1, p. 59, fig. 29. 



