370 
THE CRETACEOUS ROCKS OF BRITAIN. 
and Glyphocyphus radiatus. The following are the most charac¬ 
teristic species : — 
Cardiaster pygmaeus, Forbes (Fig 63). 
Cidaris hirudo, Sori$. 
„ serrifera, Forbes 
,, Sorigneti, Geinitz 
Cyphosoma radiatum, Sorig. 
Discoidea Dixoni, Forbes (Fig. 66). 
„ minima, Ag. 
Galerites subrotundus, Mant. (Fj . 64)* 
Hemiaster minimus, Ag. (Fig. 65). 
Holaster planus, Mant. 
Micraster corbovis, Forbes 
Salenia granulosa, Forbes 
Actinozoa.— The onty corals which have yet been found in the 
Middle Chalk, are Axogaster cretacea and Parasmilia centralis , and 
they are rare. 
Spongida.— Sponges are rare in the lower beds, but become 
common at the top of the Terebratulina zone. The following 
include those which are of most general occurrence :— 
Ceplialites Bcnettise, Mant. 
,, dongitudinalis, Smith 
Craticularia Fittoni, Mant . 
Guettardia stellata, Mich. 
Plocoscyphia convoluta, Smith 
„ flexuosa, Mant. 
Steletta inclusa, Hinde 
Ventriculites alcyonoides, Mant . 
„ decurrens, Smith 
„ impress us, Smith 
„ radiatus, Mant. 
