38 Dr. T. Wright on new Species of Echinodermata 
the anal valley is a long narrow depression extending from the 
apical disc to the margin, it has perpendicular sides and a small 
anal opening, the base is flat and only slightly depressed at the 
mouth ; the anterior and posterior pairs of interambulacra are 
moderately convex in this region, and the basal portion of 
the single interambulacrum is very slightly produced ; the mouth- 
opening is excentral, nearer the anterior margin, it has a pen- 
tagonal form with five rudimentary lobes. The surface of the 
test is covered with microscopic tubercles requiring a good lens 
to distinguish them ; these bodies are only a little larger at the 
base of the test; the apical disc is small and nearly central, its 
elements are so closely soldered together that its general form 
can alone be distinguished; the eyeholes are situated at the 
apices of the ambulacra, and the ovarial holes further outwards 
and between them, whilst the madreporiform tubercle occupies 
the centre of the disc; the test is very thin and often deformed, 
its upper surface having sometimes an irregular appearance. 
The beauty and regularity of the specimen figured forms an ex- 
ception to all the others we possess of this species. 
Affinities and differences.—Nucleolites Woodwardit most nearly 
resembles N. orbicularis, and is the only one among its Oolitic 
congeners for which it could be mistaken. The following cha- 
racters are diagnostic of N. Woodwardii. The tumidity of the 
sides and flatness of the dorsal surface, both of which are absent 
in N. orbicularis. In our species the base is flat and the mter- 
ambulacra are slightly produced, whilst in N. orbicularis the base 
is concave and the interambulacra are convex and prominent. In 
N. Woodwardii the anal valley is narrow, whilst in N. orbicularis 
it is wide ; the general outline of our species is subquadrate, that 
of the N. orbicularis is circular ; the petaloid arrangement of the 
ambulacral areas extends downwards nearer to the margin in N. 
orbicularis than in N. Woodwardii ; the narrowness of the anal 
valley in our species establishes an affinity between it and Clypeus 
altus, M‘Coy ; but the flatness of the base and the depression of 
the dorsal surface in N. Woodwardii, make a wide distinction be- 
tween it and that species, which has a high convex dorsal surface 
and extremely prominent basal interambulacra, with a greatly pro- 
duced interambulacrum ; it differs from N. Hugii in having the 
anal valley extended from the disc to the posterior margin, whilst 
in that species a portion of the test intervenes between the dise 
and the valley; the difference between N. Woodwardii and N. scu- 
tatus and N. clunicularis is so great, that it is scarcely possible 
that N. Woodwardii can be mistaken for either of these forms. 
Locality and stratigraphical range.—We have collected this 
Urchin from the Great Oolite near Cirencester and at Salperton 
Tunnel, Great Western Railway, and from beds of the same age 
