MESOZOIC llADIATA. 59 



Acf'osalenia rarispina (M'Coy). 



Sp. Char. Spheroidal, depressed ; ambulaera flat, slightly flex- 

 uous, with two rows of tubercles which towards the base are 

 large, manimillated and perforated ; interambulacra three times 

 the width of the ainbulacral spaces, primary tubercles very pro- 

 minent, nearly twice their diameter apart, placed alternately, 

 but scarcely more than two tubercles in each vertical row ; each 

 tubercle surrounded by a ring of blunt granules, and between 

 one tubercle and another numerous similar granules are scat- 

 tered. 



I think the position of the anus and the plates of the vertex 

 agree with that division of the genus to which the A. aspera be- 

 longs, but a little adhering siliceous matrix in each of the speci- 

 mens before me prevents my being quite certain. The ambulacra 

 being a little undulated also approximates it to the A. aspera^ 

 but it is a much rarer species, and easily distinguished by the 

 suigularly small number and great distance of the primary tu- 

 bercles, and the quantity of intervening granulation. Diameter 

 4 lines, height 3|- lines ; sometimes larger. 

 Bare in the great oolite of Minchinhampton. 

 {Col. University of Cambridge.) 



Hemicidaris confluens (M'Coy). 



Sp. Char. Depressed (average diameter 9 lines, height 5 lines) ; 

 ambulacra undulating, upper third narrow, gradually widen- 

 ing to the mouth ; the upper portion bears very minute 

 crowded tubercles, which gradually increase in the wide por- 

 tion, forming two alternating rows of moderately large, per- 

 forated, crenulated primary tubercles with many intervening- 

 blunt granules ; interambulacral spaces twice as wide as the 

 ambulacral, with two rows of very large primary tubercles, 

 only four to five in a row, the smooth bases of which are ver- 

 tically confluent (not separated by rows of granules), two ver- 

 tical rows of small granules between the tubercles. 



The only species this can be confounded with is the H. Thur- 

 mani (Ag.), which it resembles in its depressed form and very 

 few large tubercles, and in the small size of the tubercles on the 

 interambulacral spaces, but in this species the ambulacra widen 

 more and the primary tubercles on them are larger ; while each 

 of the primary interambulacral tubercles in that species is sepa- 

 rated from the next above and below by several rows of granules, 

 while they are confluent, so to speak, in the present. 



Rare in the great oolite of Minchinhampton. 



(Col. University of Cambridge.) 



