Vol. 51.] RADIOLARIA.N KOCKS IN THE LOWER CULM MEASURES. 657 



other cephalopod ] is Orthoceras striolatum, Sandb., a species also 

 occurring in the Lower Culm of Germany. Besides these, there 

 are four species of Phillipsia, three of which also pass up into the 

 Codden Hill Radiolarian Beds ; three species of brachiopods, one of 

 which is found in the Codden Hill Beds ; and several species of 

 lamellibranchs, including Posidonomya Becheri, the only form in 

 common with the dark limestones and shales below. The presence 

 of the trilobites shows that these Goniatites spiralis-shales are more 

 nearly related to the Eadiolarian Beds than to the underlying 

 Posidonomya-be&s. 



As possible equivalents of the dark Posidono7ny a-]im.estones and 

 shales of Venn, Swimbridge, etc., De la Beche considered 2 the 

 massive bluish limestones with intercalated cherty beds and asso- 

 ciated reddish shales which form the conspicuous ridges of West- 

 leigh, Canonsleigh, and Holcombe Bogus in North-east Devon. 

 They are very different in appearance from the Posidonomya-xoeks 

 and resemble in general characters the ordinary types of Carbon- 

 iferous Limestone, so that they might almost be regarded as a local 

 development of this rock, which comes in here between the Devonian 

 and the Culm Measures in much the same way as in the Rhine 

 Province near Diisseldorf referred to by Dr. Kayser. 3 In addition 

 to foraminifera and species of corals and brachiopods which also 

 occur in the Carboniferous Limestone, these beds likewise contain 

 two species of cephalopods : Goniatites mixolobus, Phill., and G.spir- 

 orbis, Phill., which are present as well in the Codden Hill Eadio- 

 larian Beds, and the cherty portions of the beds also show casts of 

 radiolaria. The only species common to these limestones and the 

 dark Posidonomya-be&s to the westward are P. Becheri and 

 P. lateralis, Sow. 



The Badiolarian (Codden Hill) Beds are next higher in the series, 

 but their junction with the beds below has been seldom observed. 

 At Wooladon, near Launceston, they rest upon the Posidonomya- 

 be&s ; in other parts of this and the Tavistock district Mr. Ussher * 

 states that below them are beds with Goniatites spiralis. At 

 Bamshorn Down the same author 5 considers that they are at the 

 base of the Culm and even below the Posidonomya-be&s, but definite 

 junctions are not exposed. Excluding the radiolaria, 25 species have 

 been recognized in these beds, a greater number than in any of the 

 other divisions. Only 7 of these occur in the other divisions of 

 the Culm Series in this country, while 8 are known as well from 

 the Lower Culm of Aprath and Herborn in Germany, and a similar 

 number are likewise present in the Carboniferous Limestone of the 

 British Islands and Belgium. The distinguishing features of the 



1 We have been unable to verify the occurrence in these beds of Goniatites 

 mixolobus and G. sphtzricus as stated in 'Mon. Oarb. Trilobites/ Pal. Soc 

 1883-84, p. 64. 



2 ' Eeport Geol. Cornwall, etc.' 1839, p. 105. 



3 Jahrb. d. konigl. Preuss. geol. Landesanst. f. 1881, p. 52. 



4 Proc. Som. Archaeol. & Nat. Hist. Soc. vol. xxxviii. (1892) p. 129. 



5 Ibid. p. 134. 



