from the Lias and Oolites. 321 



the anal valley is a long narrow depression extending from tlie 

 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 interarabulacrum 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 Woodwardii most nearly 

 resembles A^. 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 inter- 

 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. Woodwar-dii ; the narrowness of the anal 

 valley in our species establishes an affinity between it and Clypeus 

 alius, 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 diff'ers from iV. 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 disc 

 and the valley; the diff^crence 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 llailway, and from beds of the same age 



Ann. ^ Mag. N. Hist. Ser. 2. Vol. xm. 21 



