A. J. Jukes-Browne — Ttro Stages in Upper Chalk. 865 



stages is very apparent, but there is a transition from one Echinoderm 

 fauna to the other, and the zone might be placed in either stage. 



Lastly, Table VI shows the distribution of the Eehinoids and 

 Crinoids through the same zones in England, and in compiling this 

 I have received special assistance from Mr. A. W. Eowe, who has 

 kindly sent me notes regarding the identification and range of all the 

 species, so that this list is more correct than any that has previously 

 been published. 



In comparing this with the preceding lists it will be noticed that 

 the number of species is less and that the proportion of them which 

 ranges from the lower to the higher zones is greater. Both these 

 peculiarities are doubtless owing to the fact that in England tliere is 

 little variation in the lithological character of the Upper Chalk, the 

 whole of it being a deep-water facies of the formation deposited under 

 conditions which did not change greatly from beginning to end. 

 There was, therefore, no sudden or rapid extinction of species, only the 

 increasing rarity of some and the occasional introduction of new forms. 



In spite of these conditions there are many species which do not 

 I'ange from the lower to the higher zones. The total number of 

 species and varieties enumerated is fifty-one, and of these forty-four 

 occur in the lower four zones and twenty-five in the two higher 

 zones, nineteen species being common to the two assemblages. This 

 is less than half of the larger fauna, so that there is still a considerable 

 difference between them. The zone of 0. pihila has yielded twenty- 

 seven species, of which seventeen range both up and down, only two 

 have an exclusively upward range, while eight do not range higher ; 

 it is therefore more closely connected with the lower than the 

 higher zones. 



TABLE VI. 



ECHINODERMS IN ENGLAND. 



Species. 



Cidaris hmido, Sorig 

 C. sceptrifera, Mant. . 

 C. clavigera, Koenig . 

 C. perornata, Forbes . 

 C. siihvesiculosa, d'Orb. . 

 C. Merceyi, Cotteau . 

 C. serrifera, Forbes . 

 C. serrata, Desor . 

 C. pleracantha, Ag. . 

 CypJiosoma Koenigi, Mant. 

 C. corollare, Ag. 

 C. granulosuvi, Goldf. 

 C viagnificum, Cott. 

 C. elongakim, Cott. 

 C. radiatum, Sorig 

 C. spatuliferwn, Forbes . 



