Some new Upper Greensand Echinoderms. 19 



one from another. On the upper part of the test, the suture 



between the interambulacral rows of plates is impressed. 

 Lat. |i inch; oral apert. ^~ inch; apical apert. ~ by -^ inch. 



Coll. University Museum. 



I cannot conceal from myself a suspicion that some of the 

 characters here described are a monstrous development. No- 

 thing, however, is wanting in the anatomy of the test, nor is 

 anything unnatural superadded. The only really abnormal 

 character is the unsymmetrical ambulacral ornament arising 

 from the coalescence and development of granules into large 

 tubercles. If this character is not generic, it can only be an 

 individual variation : if it should prove to be the latter, the 

 genus would have characters probably indicating its place to be 

 among the Saleniadse. 



Diadema fungoideum. 



Test circular; inflated on the lower part, obliquely depressed 

 above, thus appearing rather subcorneal. Base rounded, on its 

 inner part concave ; oral aperture deeply sunk and larger than 

 the apical disk. Ambulacral spaces two-thirds the width of the 

 interambulacra ; furnished with two rows of tubercles, which 

 are very large round the circumference and become less elevated 

 and rapidly smaller above, and regularly smaller below : those 

 of the circumference and base are of the same size as the corre- 

 sponding interambulacral tubercles ; those of the upper surface 

 much smaller. Each row consists of about eight. Round the 

 circumference the rows are separated by a single zigzag line 

 of granules. On the upper part the pairs of pores are close 

 together, but in the middle they become wider apart, and are 

 separated by a granule, which renders their detection difficult. 

 The space between them and the tubercles is granulated. 

 The interambulacral tubercles are very large and close toge- 

 ther, in two straight rows of eleven each ; on the upper part 

 they are but slightly smaller than at the circumference; sepa- 

 rated by wide spaces, which are occupied by two somewhat 

 irregular rows of granules. On the outside of the tubercles 

 round the bend of the base are two or three very small acces- 

 sory tubercles. Each pair of pores is enclosed in a little, 

 oblique, elevated, oval ring. On the base the interambulacral 

 areas are noticeably inflated. 



Lat. || inch, alt. ^ inch ; apical disk 7 \ inch. 



This very distinct and remarkable little species is most nearly 

 related to D. Carteri (Woodw.), from which it is distinguished 

 by its subcorneal shape, absence of secondary tubercles, difference 

 in size and number of primary tubercles and granulations, &c. 



Very rare. Coll. University. 



2* 



