Vol. 51.] RADIOLARIAN ROCKS IN THE LOWER CULM MEASURES. 643 



Of the 23 genera enumerated above, 21 have been previously 

 determined from the Palaeozoic formations of this country and the 

 continent, the larger proportion — 17 genera — from the Culm of 

 Germany, Sicily, and Russia by Dr. Rust. Of the other 2 genera, 

 one (Trigonocyclia) has not previously been recognized below the 

 Jurassic, and the other (SetJiodiscus), although a very simple form, 

 does not seem to have been hitherto met with in the fossil state. 



VIII. Description of the other Fossils associated in the sahe 

 Rocks with the Radiolaria. 



The Radiolarian or Codden Hill Beds of the Lower Culm Measures 

 have hitherto been considered as practically unfossiliferous, and 

 indeed their distinctive characters have been attributed to meta- 

 morphism. 1 Prof. J. Phillips, 2 however, who appears to have himself 

 very diligently searched these rocks, described and figured from 

 them the following 5 species: — Turbinolopsis pauciradialis, Phill., 

 Leptcena mesoloha, Phill., Terebratula (Atrypa) insperata, Phill., 

 Goniatites mixolobus, Phill., and Cyathocrhius distans, Phill., this 

 last being merely detached joints of crinoid-stems. The other fossils 

 which Phillips described in the same work from his so-called ' Car- 

 bonaceous group ' 3 did not come from the Radiolarian or Codden 

 Hill rocks, but from the dark limestones and shales underlying them 

 at Swimbridge, Venn, Bampton, etc., in North Devon, and at Trus- 

 cott, Lew Trenchard, and other localities in Cornwall and South 

 Devon. The fossils enumerated by Mr. Lssber, in his 'British 

 Culm Measures,' 4 from the Basement Beds of the Culm do not 

 appear to include any at all from the Radiolarian or Codden Hill 

 Beds ; those given are from beds at Waddon Barton and other 

 places in the Chudleigh district discovered and determined by Dr. 

 Henry Woodward and Mr. R. Etheridge, Jun., in the celebrated 

 shales with trilobites, in which no radiolaria have as yet been met 

 with, and which are probably at a slightly lower horizon than the 

 Codden Hill Radiolarian Beds. 



Certain thin beds, however, in the Radiolarian series at Codden 

 Hill and its neighbourhood, and also west of the Taw river near 

 Barnstaple, contain a fairly varied but scanty fauna in addition 

 to the radiolaria, and in view of the importance of these fossils in 

 determining the geological horizon of the radiolarian rocks, and 

 since many of them have not hitherto been recorded from this 

 country, we give below detailed references to them. These fossils 

 do not seem to be generally distributed in the Radiolarian rocks ; 

 so far they have been met with only in limited thin bands Of 

 whitish or yellowish soft shaly or platy rock, in which radiolarian 

 casts are also abundant. With hardly an exception the calcareous 



1 Proc. Som. Archseol. & Nat. Hist. Soc. vol. xxv. (1879) pt. ii. p. 5 ; also 

 T. M. Hall, ' Sketch Geol. Devon.,' (White's Gazetteer), 1878, p. 9, reprint. 



2 ' Palaeozoic Fossils of Cornwall, etc.,' 1841. 



3 Ibid. pp. 189, 194. 



4 Proc. Som. Archseol. & Nat. Hist. Soc. vol. xxxviii. (1892) pp. 159-161. 



