Fossils of the Chazy Limestone 451 



De Orbigny. — This author thinks Scalites allied to Straps 

 rollus, and only differing therefrom by having the umbilicus 

 closed. He quotes Raphistoma as a synonym.* 



Pictet places Scalites among the Trochidce, and thinks that if 

 Raphistoma is to be retained it must be differently defined.f 



F. Roemer refers Scalites to the genus Euomphnlus, and says 

 that Raphistoma differs from Scalites only in having the spire 

 more depressed.]; 



S. P. Woodward makes of Scalites a sub-genus of Pleuroto- 

 maria. He cites Raphistoma as a synonim.§ 



Salter has given to Scalites the rank of a genus, and he makes 

 Raphistoma a sub genus, which would include all such species as 

 P. qualteriatus, P. lenticularis, &e., &c.j| 



It must be observed that in forming their respective opinions, 

 the above-named eminent Naturalists and Palaeontologists had not 

 before them specimens such as P. docens, exhibiting a well-defined 

 spiral band. 



Our collections confirm the opinion of Mr. Woodward, but I 

 do not think it convenient to retain Scalites even as a sub-genus; 

 because, as I shall shew hereafter in another publication, the- 

 transition from Scalites angulatus to such forms as P. rotuloides 

 (Hall) is so gradual, through a perfect series of species, that, to 

 determine whether certain forms should be placed in the genus or 

 sub-genus, will be next to impossible, and occasion an useless 

 expenditure of time and mental labour. When the lines between 

 groups become so excessively inconvenient, they should be blotted 

 out altogether. For the present, therefore, I shall place all our 

 species in the genus Pleurotomaria. Judging from the number 

 of species in the Canadian rocks, I think there must be a great 

 many others in the extensive private or public collections of 

 Lower Silurian fossils in the Western and Southern States; and 

 until all these are described and figured we cannot have all the 

 facts before us upon which the classification must be ultimately 

 founded. 



On examining the numerous species of Euomphalus or Schizos- 

 toma, figured and described in the works ofGoldfuss, DeKoninok, 



* Prodrome de Paleontologie. Vol. 1, p. 7. 

 f Traite de Paleontologie. Vol. 3, p. 153. 

 t Bronn's Lethaea Geognostica. Vol. 1, 456. 

 § Woodward's Recent and Fossil Shales, p. 147. 

 || Salter, Canadian Fossils, Decade 1, p. 10. 



