160 Dr. T. Wright on the Cidaridse of the Oolites. 



Goniopygus (?) perforatus, Wright, n. s. PI. VI. fig. 5 a, b. 



Test spheroidal, depressed; ambulacral arese with two rows of 

 small tubercles ; interambulacral arese with two rows of nearly 

 equal-sized primary tubercles, each surrounded by a circle of 

 granules ; tubercles perforated. 



Height yyths of an inch, transverse diameter T 6 (jths of an inch. 



Description. — The ambulacral arese of this little anomalous 

 Urchin carry small marginal tubercles increasing in size towards 

 the base of the arese, and having a few granules interspersed be- 

 tween them. The interambulacral arese are about twice and a 

 half the width of the ambulacral, and furnished with two rows of 

 tubercles from seven to eight in each row. The tubercles are 

 raised on mammillated eminences which are destitute of crenu- 

 lations ; the summit of the tubercles is slightly perforated, they 

 detach themselves in a well-defined manner from the surface of 

 the test and are very uniform in size, and each mamma is en- 

 circled by a distinct wreath of small granules. There are a few 

 other granules studding the plates besides those forming the 

 boundary circles of the areolse. The apical disc is absent ; the 

 mouth is large and deeply notched. 



Affinities and differences. — I have placed this Urchin provi- 

 sionally in the genus Goniopygus, as it comes nearer to the cha- 

 racters of that form than any other. Agassiz states in his Cata- 

 logue that the tubercles are imperforate, but this character is not 

 alluded to in his 'Echin. Foss/ The absence of crenulations 

 from the mammse, the nearly uniform size of the tubercles, the 

 distinctness with which they stand out from the test, and a frag- 

 ment of the angular apical disc in situ, seem to justify the sup- 

 position of its being Goniopygus; but the perforations in the 

 tubercles make the exception, and suggest the query whether the 

 absence of perforations is a generic or only a sectional character. 

 The specimens before me, the only three yet found, are so im- 

 perfect, that I write with much reserve regarding them ; they may 

 perhaps prove to be the young tests of Pedina, in which we have 

 observed that the pores change from simple pairs to triple oblique 

 pairs with age, and the crenulations of the mammse can scarcely 

 be seen. 



Locality. — I collected these Urchins from the Pea- grit of 

 Crickley Hill with Acrosalenia Lycetti and small Bryozoan poly- 

 pifera. 



The Echinidje* 



Have a thin test, and are distinguished from the Cidaridse and 



* The group of Echinida includes twenty-three genera: Astropyga,Gvo.y ; 

 Diadema, Gray ; Hemidiadema, Agass. ; Cyphosoma, Agass. ; Echinocidaris, 



