REPORT OF THE STATE PALEONTOLOGIST 1902 945 



in the fact that the relations of the Tremadoc to the Cambric, 

 on account of the frequency of the Olenidae and Lingulellae in 

 the former, are more striking than those of the Ceratopyge 

 beds to the Olenus shales in Scandinavia. 



Professor Brogger's careful revisions of the determinations 

 of the English paleontologists [see his two works cited before] 

 leave however little doubt, that, as Brogger concludes, the 

 Tremadoc is to be correlated with the Ceratopyge beds, and 

 hence the Dictyonema shale is to be regarded also in Britain as 

 the terminal member of the Cambric series. The Dictyonema 

 beds of the Malvern hills overlie the " Dolgelly group " and are 

 placed by Callaway 1 below the " Shineton shales ". The latter 

 are considered by the same author as transitional between the 

 Lingula flags and the lower Tremadoc, and thus still placed 

 with the Cambric. Brogger, however, subjects the genera of 

 the " Shineton shales " to a revision 2 and thus finds the latter 

 to be equivalent to a horizon between the Dictyonema bed of 

 Norway and the Ceratopyge limestone, approximately to his 

 3 a«— 3 a# thus transferring them into the Lower Siluric. 



The Tremadoc of north Wales has been worked out by Salter. 3 

 Brogger concludes as to the Tremadoc of North Wales (in " Ueber 

 die Verbreitung etc." p. 42) that its largest part is equivalent 

 to the Ceratopyge limestone horizons 3 a« — 3 ar, that the 

 lowest part of the Tremadoc (with Dictyonema flabel- 

 1 i f o r m e ) corresponds already to his zone 2 e, the Dictyo- 

 graptus slate of Christian ia, while the uppermost part is per- 

 haps equivalent to his 3 b, the Tetragraptus-Phyllograptus slate 

 of Christiania. 



The Tremadoc beds of south Wales (St Davids and Ramsay 

 island) have become known, specially by the investigations of 

 H. Hicks. 4 They differ considerably from the development in 

 north Wales and in Norway, consisting of more than 1000 feet 

 of gray, flaggy sandstones (St Davids) with few trilobites and 



1 On a New Area of Upper Cambrian Rocks in South Shropshire, with a 

 Description of a New Fauna, Geol. Soc. Quar. Jour. 1877, 33: 652 ff. 



2 Stages 2 and 3, p. 144-46. 



9 Mem. of the Geol. Sur. 1866. v.3. See edition of 1881 by Etheridge. See 

 also A Monograph of British Trilobites (1864-83) in Pal. Soc. and Cat. of Camb. 

 and Silur. Fossils. 1873. 



* Geol. Soc. Quar. Jour 1873. 29: 39 ff. 



