400 Mr. F. M^Coy on some new Mesozoic Radiata. 



stantly from specimens I have examined of the Astrcea sexradiata 

 (Gold.) which agree with his figure in having them half their 

 diameter apart, without perceptible variation, while from the 

 A. tumularis (Michel.) it differs in its smaller and less promi- 

 nent cells as well as form of the mass. 



Not uncommon in the inferior oolites of Dundry. 



[Col. University of Cambridge.) 



Astrcsa (Lamk.). 



From the unfavourable mode of petrifaction of the oolitic 

 Astrcea, I am unable to seize their subgeneric characters with the 

 precision I could wish — their specific characters are easy enough 

 — I have therefore provisionally been obliged to leave them all 

 under the old genus Astraa for the present, being unable satis- 

 factorily to define their differences from the recent group. 



Astrcea tenuistriata (M'Coy). 



Sp. Char. Corallum forming irregular flattened masses, of shal- 

 low polygonal cells, very unequal in size and shape (most 

 usual diameter about 5 lines) ; centre obscurely granular, ra- 

 diating lamellse very slender, close, minutely crenulated, alter- 

 nately larger and several shorter (number varies with the size 

 of the star, but always about twelve in a space of two lines at 

 the margin). 



In the very irregular size and shape of the stars and the great 

 number and delicacy of the lamellfe, this agrees with the A. con- 

 fiuens (Gold.), from which it differs in the flatness of the cells, 

 and in wanting the remarkable confluent character of that spe- 

 cies, the young cells developing their boundary ridges almost on 

 their first appearance. 



Common in the inferior oolite of Dundry. 



[Col. University of Cambridge.) 



Astrcea explanulata (M^Coy). 



Sp. Char. Corallum forming flat expansions, of nearly equal, 

 subrhomboidal, shallow cells, averaging 2 lines in diameter ; 

 radiating lamellre from twenty-six to thirty, thick, very ob- 

 scurely punctured or crenulated, about every third one reach- 

 ing to the impressed central point ; interstices very obtusely 

 angular. 



In the flat form of gi'owth assumed by the masses, and in the 

 equalit}^, shallowness and tetragonal form of most of the cells, 

 this strongly resembles the A. explanata (Gold.) of the Natheim 

 oolite ; but on comparison with authentic specimens of this latter, 

 I find the cells of our species average only half the diameter of 



