from the Lias and Oolites. 319 



tubercles on each side of the margins of the area^ between these 

 are several rows of small granulations arranged without much 

 order ; at the base of the area ten larger tubercles are disposed 

 in pairs, the tubercles on the right side alternating \A-ith those 

 on the left ; the interambulacral areas are about twice the width 

 of the ambulacral ; a single row of tubercles occupies the centre 

 of each of the two columns of plates, and numerous smaller 

 tubercles degenerating into mere granules cluster around the 

 base of the large tubercles ; a second row of tubercles extends 

 upwards from the basal angle towards the equator, where it ter- 

 minates ; the basal tubercles consisting of about six pair occupy 

 all the base of the area — they are about the same size as those 

 of the ambulacra ; but are arranged somewhat less regularly 

 The median depression in the centre of the interambulacra is 

 very well marked in this species, so that the test has the appear- 

 ance of being divided into fifteen lobes. The anal plates form a 

 prominent narrow ring around the oblong anal opening, and the 

 eye-plates are closely soldered to them ; the eye-holes are very 

 distinct in most of our specimens. The mouth-opening is of 

 moderate size, and is slightly decagonal ; the poriferous avenues 

 lie in considerable depressions of the test, which throws the am- 

 bulacral areas into prominent relief from the interambulacra. 



Affinities and differences. — The marginal rows of tubercles on 

 the ambulacra, and the central rows of tubercles on the plate 

 columns of the interambidacral areas serve to distinguish this 

 species from P. nodulosus. It has a considerable resemblance to 

 the young forms of Echinus germiyians, but the regularity of the 

 rows of tubercles on the sides and upper surface of the test, 

 and the size and arrangement of those at the base afford good 

 diagnostic characters by which it may be easily distinguished 

 from that common form ; the same group of characters serves to 

 distinguish it from Arbacia Forbesii. 



Locality and stratigraphical range. — We have only found this 

 species in the Pea-grit of Crickley Hill ; all the other specimens 

 that were collected by JMr. Gibbs of the Geological Survey, were 

 found in the same bed of this locality. 



We dedicate this fossil to Professor Deslongchamps of Caen, to 

 whom palaeontology is indebted for many important contribu- 

 tions to the Oolitic fauna published in the ' Alemoires de la 

 Societe Linneenne de Normandie.' 



g. i), a-e. 



Nucleolites Woodwardii, Wright, 1852. PI. XII. fi 



Test subquadrate, sides tumid, dorsal surface flatly convex, anal 

 valley deep, narrow and spear-shaped, extening from the 

 apical disc to the posterior border ; ambulaci*al areas narrowly 



