78 



CIDARIS 



in connection with the tubercle adjacent to the anal margin ; h that on the next tubercle, 

 counting downwards ; c that beneath h ; and ^that below c, on the tubercle which is the third 

 from the peristome : a is in length five tenths of an inch, in diameter three tenths ; d is in 

 length two tenths of an inch, in diameter one twentieth. The test from which these spines are 

 derived is five twentieths of an inch in height, and nine twentieths in transverse diameter. 



Fig. 4. 



a. L. c. d. 



Spines of Cidaris BowerlanTcii ; magnified two diameters. 



" Several of the spines of this species from different localities are figured on PI. XIII ; 

 figs. 9, 10, and 11 are from Folkestone, figs. 13 and 14 from Cambridge, 8 from near 

 Arundel, from which last-mentioned locality also come the plates of C. dissimilis, figured 

 PI. XIII, figs. 6 «, 6 ^. In all these a certain variation in general form is very perceptible. 

 " Cidaris Bowerbankii has great affinities in its test with C. clavi(jera, but is always 

 much smaller in size. It is a very rare species. The horizon of C. Bowerbankii at 

 Polkestone is just above the Upper Greensand. 



" At Folkestone, in company with the spines of C. Boioerbankii, occur globose spines 

 with a short neck, and having the body covered with coarse spiny projections arranged 

 longitudinally. They are drawn of the natural size in the woodcut fig. 5 ; they appear 

 to differ from C. velifera, and are perfectly distinct from the spines of C. Bowerbankii. 



Fig. 5. 



a. b. c. 



Spines of a Cidaris from the Lower Chalk at Folkestone; natural size. 



"Additional Note on the CIBABE/S vrom the Red Chalk. (See p. 44.) 



" In the thin red-coloured band met with at Hunstanton, in Norfolk, and in the lowest 

 of the pink-coloured beds at Speeton, in Yorkshire, occasionally occur elongate, cylindrical 



