from the Lias and Oolites. 37 
lanceolate ; posterior lobes short and truncated ; base flat ; 
antero-interambulacra and postero-interambulacra _ slightly 
swollen at their base; the single ambulacrum scarcely pro- 
duced ; mouth-opening pentagonal, situated anteriorly ; apical 
disc small and nearly central. 
Height ,5,ths of an inch, antero-posterior diameter 1 inch and 
’ 5th, transverse diameter 1 inch and ;%,ths; the larger speci- 
mens are so much deformed by pressure that their proportional 
dimensions cannot be accurately given. 
Description —Some individuals of this species were formerly 
considered by us to be only varieties of Nucleolites orbicularis, 
Phil., but a better knowledge of the structure of this Urchin, 
derived from the study of a series which we collected last summer 
and have carefully compared with good typical examples of N. or- 
bicularis, leaves no doubt about the distinctness of N. Woodwardii 
from that Cornbrash form. The test is thin and not often suffi- 
ciently well preserved for determining the species; the one which 
we have figured is a small but a very perfect specimen, it has a 
subquadrate outline and is 4th of an inch broader than it is in 
the antero-posterior diameter ; it is slightly narrower anteriorly 
than posteriorly, and (which is more apparent when it rests upon 
its dorsal surface) the posterior margin is seen to be broadly 
truncated ; the sides are tumid, sometimes irregularly so, and 
the test is higher across the apices of the postero-lateral ambu- 
lacra than at any other point ; the tumidity of the sides produces 
a greater flatness of the dorsal surface than we observe in any 
other of the small Nucleolites of the Oolitic rocks; the ambu- 
lacral areas are nearly all of the same width, they have a narrow 
graceful lanceolate form, from the mouth to about midway 
between the margin and the apical disc, they are nearly of equal 
width ; at this point the pores gradually change their form, and are 
slightly separated apart for a short distance, and begin again to 
converge as they approach the disc ; the internal row are circular, 
the external in the form of oblique slits, the widest part of which 
is outwards, the circles are formed by notches in the upper and 
under sides of the small ambulacral plates, and the oblique slits 
by uncalcified portions of the margins of the same-plates ; from 
the termination of the petaloid portion of the ambulacral areas 
to the mouth, the pores are small and set wider apart, whilst 
the diameter of the areas remains about the same; near the 
mouth-opening they are again more closely crowded together, 
and terminate in arches the convexity of which look towards 
that aperture ; the interambulacral areas are of unequal width ; 
the anterior pair are the narrowest, the posterior pair are wider 
than the anterior, and the single interambulacrum ia the widest ; 
