634 BR. G. J. HINDE A.KD MR. HOWARD FOX ON [Nov. 1 895, 



finding any specimens in which their structural characters are satis- 

 factorily preserved. In the large majority of the Culm siliceous rocks 

 the radiolaria are now in the condition of solid casts of the original 

 forms ; their skeletal walls have entirely disappeared and the indi- 

 vidual casts are only bounded by the siliceous matrix of the rock and 

 without definite even outlines. In such instances, only the size and 

 general form, with the radial spines, can be distinguished. 



In some of the hard cherty and platy rocks of Ramshorn Down 

 and the Chudleigh district the radiolarian tests have been stained of 

 a brownish or amber tint, so that the lattice-like structure can be 

 seen ; but they are now so crushed and obscured in a confused mass 

 of broken spines and fragmental debris that it is seldom that a spe- 

 cimen is sufficiently clear to be figured. In other instances the silica 

 of the test is of a pinkish tint, and thus distinguishable from the 

 clear silica surrounding it. For some not apparent reason the tests 

 thus preserved nearly all belong to discoidal forms of Lithocyclia and 

 Porodiscus. 



The radiolaria in the soft, incoherent, shaly beds are in much the 

 same state of preservation as those in the harder cherty rocks — that 

 is, they are mostly casts, and the original tests have been either dis- 

 solved or if preserved they cannot in sections be distinguished from 

 the infilling silica. 



With radiolaria thus imperfectly preserved determination is 

 extremely difficult ; in only a very few instances, as in some of the 

 Discoidea, has it been possible to recognize specific characters ; with 

 respect to many, even the generic determination has been a matter of 

 inference. It can be seen that a considerable variety of forms are 

 present in these rocks, and the following Orders are represented — 

 Beloidea, Sphseroidea, Prunoidea, Discoidea, and Cyrtoidea — by 23 

 genera. Both in the number of the forms and in their state of 

 preservation the radiolaria in our Culm Measures fall far short 

 of those which Dr. Rust has described x from the corresponding 

 formations in the Blarz, Sicily, and Russia. Most of these, however, 

 were obtained from two or three small nodules in which the minute 

 structure of the tests was preserved, and should specimens in similar 

 condition be met with in our rocks they would probably be found to 

 contain equally as many species. 



Subclass SPUMELLARIA, Ehrenberg. 



Order BELOIDEA, Haeckel. 



Genus Sph^rozot/m, Meyen. 



PI. XXV . figs. 1 a-\ g. In this genus there is no latticed test ; 

 the skeleton consists of free siliceous spicular bodies, which are now 

 found detached in the rock. According to Dr. Riist 2 the spicules 

 have four rays extending from a common centre at angles of 120°; 



1 ' Palseontographica,' vol. xxxviii. (1892) pp. 107-192, pis. vi.-xxx. 



2 Ibid. p. 133. 



