OO MESOZOIC RADIATA. 



with many small, irregularly placed intervening granules ; 

 three oblique pairs of pores in each row ; ovarian and ocular 

 plates as in the genus generally. 



The two rows of large tubercles in each area, with the very 

 minute intervening granules, distinguish this species from its con- 

 geners. It is most closely allied to the E. fallax and E. serialis 

 (Ag.), but is well distinguished by the almost complete absence 

 of secondary tubercles as well as the greater size of the primary 

 ones, and the more pentagonal form of the disc, in which it ap- 

 pi-oaches the E. excavatus (Gold.), from which it equally differs 

 by the above characters. 



Occurs in the coral rag of Malton and in the great oolite of 

 Minchinhampton. 



[Col. University of Cambridge.) 



Arbacia inflata (M^Coy). 



Sp. Char. Oblate-spheroidal (diameter 6 lines, height 4| lines), 

 margin of the base tumid, rounded ; ambulacra flat, depressed, 

 slightly less than half the width of the interambulacra, the 

 pores forming very narrow rows of one pair each, the space 

 between the lines of pores with four to six very unequal, irre- 

 gular rows of small granules ; interambulacral spaces tumid, 

 with a slightly impressed, narrow, smooth line down the mid- 

 dle of each ; each interambulacral space contains about six- 

 teen rows of minute tubercles, of which the two middle rows, 

 or that bordering on each side the sutural line, are largest ; 

 under the lens the tubercles are distinctly arranged in trans- 

 verse rows, eight on each interambulacral plate, touching each 

 other without intervening granules, but between one plate and 

 the next above or below (or between the rows) there are a few 

 minute granules, generally arranged in one or at most two 

 irregular rows. 



Distinguished from the A. pilos (Ag.) by its more depressed, 

 inflated form, rounded margin of the base, the outer* row of am- 

 bulacral tubercles not being largest, and the greater number of 

 tubercles in both area?, as well as the central smooth line of the 

 interambulacra; the A. granulosa (Miinst. sp.) is much more de- 

 pressed, has the ambulacra wider and more convex, the interam- 

 bulacra more deeply divided, and a much greater number of tu- 

 bercles in the transverse rows, which latter are separated by very 

 numerous crowded granules. 



Not uncommon in the upper greensand of Cambridge. 

 [Col. University of Cambridge.) 



* By " outer " T here mean, adjoining the anjhnlacra, without intending 

 to deny that the nnesial line may be the true exterior. 



