FROM THE CORALLINE OOLITE. 131 



Oolite of Wilts. The specimen figured in PI. VIII, fig. 1, was collected in the neighbour- 

 hood of Calne, It is more abundant in the Coralline Oolite of Yorkshire. Many fine 

 specimens having been obtained from Malton and its vicinity. Its foreign distribution 

 occupies a wide area in France. It is found in the " Corallien etage of Besangon, Saint- 

 Mihiel, La Rochelle, Druyes (Yonne), and Commercy (Meuse) ;" and in Switzerland in the 

 neighbourhood of Soleure. It is everywhere a very characteristic fossil of the Coral Rag. 



PsEUDODiADEMA RADIATA, WrigU, uov. sp. PI. VII, fig. 3 a, h, c, d, e,f. 



Test circular, depressed, inflated at the sides; ambulacra! areas narrow, with two 

 rows of primary tubercles, twelve in each row, rather smaller than those of the inter- 

 ambulacra ; poriferous zones straight, pores unigeminal throughout ; inter-ambulacral areas 

 with two rows of primary tubercles, twelve in each row, separated by a wide miliary zone 

 filled with several rows of granules; base concave, mouth opening small, peristome 

 unequally decagonal. 



Dimensions. — Height, rather more than seven twentieths of an inch ; transverse 

 diameter, nine tenths of an inch. 



Description. — The test of this species is circular, and nearly equally depressed on 

 the upper and under surface (fig. 3 c) ; the sides are rather tumid, and the ambulacral 

 tubercles are only a little smaller than those of the inter-ambulacral. The ambulacral 

 areas form no prominence on the sides as in so many other Pseudodiademas (fig. 3 a) ; 

 they are more than half the width of the inter-ambulacral ; and are occupied by two rows 

 of primary tubercles (fig. 3 d, e), of which there are twelve in each row; their bosses are 

 small, and set closely together, and their summits have well-marked crenulations (fig. 3/) ; 

 down the centre of the area there is a single zigzag line of granules, which becomes double 

 about the middle of the area ; transverse branches of granules separate the areolas ; the 

 tubercles are of a very uniform width throughout, and diminish gradually in size towards 

 both ends of the area. 



The poriferous zones are narrow, and nearly straight, and the pores are unigeminal 

 throughout ; the pores forming a pair are contiguous, with thin septa ; there are three 

 pairs of pores opposite the ambulacral plates, and four pairs of pores opposite one of the 

 inter-ambulacral plates (fig. 3/). 



The inter-ambulacral areas are not quite twice the width of the ambulacral ; they have 

 two rows of primary tubercles, of which there are twelve in each row (fig. Sd) ; each plate 

 (fig. 3/) is occupied by a wide areola, the boss is not prominent, its summit is marked 

 with twelve crenulations, and the spinigerous tubercle is small, flat, and finely perforated 



