from the Lias and Oolites. 39 
near Pewsdown, Gloucestershire, and near Burford, Oxon; it has 
likewise been found near Minchinhampton : as far as we know, 
it appears to be a Great Oolite species. 
We dedicate this species to our friend Mr. S. P. Woodward, of 
the British Museum, to whose kindness we are much indebted for 
the privilege of comparing our specimens with the magnificent 
series of Echinodermata under his care, and which he has ren- 
dered so valuable for reference by a systematic classification and 
a correct nomenclature. 
Nuceleolites Michelini, Wright. Pl. II. fig. 6, a-c. 
Test circular or oblong, discoidal and much depressed, posterior 
border produced, traneated and slightly deflected in old in- 
dividuals; ambulacral areas narrowly lanceolate ; pedal pores 
closely set together, vertex and apical disc nearly central ; 
anterior half of the dorsal surface convex, posterior half much 
declined from the vertex to the posterior border ; anal valley 
narrow above, diverging below, extending from the apical disc 
to the border; base flat, slightly concave ; mouth excentral, 
margin with five small lobes ; postero-lateral interambulacral 
areas slightly tumid at the base. 
Height =%,ths of an inch, antero-posterior diameter 3 inches 
and ;%;ths, transverse diameter 2 inches and -2,ths of an inch. 
Description.—The outline of this Urchin varies in different 
individuals, and it likewise varied at different periods of life in 
the same individual ; its most typical form is oblong, convex an- 
teriorly, produced and truncated posteriorly, and swollen out in 
the region of the postero-lateral interambulacra ; in others the 
circumference is nearly circular, and in some it is transversely 
oval ; the first form is we think characteristic of adult life, as the 
production and truncation of the single interambulacrum were 
markedly shown in the only two large specimens of this rare 
species which we have seen 5 in all the test is very flat, the ante- 
rior half is gently and nearly equally convex, the posterior half 
is sloping and much declined in the direction of the posterior 
border. The ambulacral areas are narrow, the anterior one most 
so; the antero-lateral and postero-laterals are about the same 
width, they have a lanceolate form, and are composed of very 
narrow plates ; about =%;ths of an inch above the margin, the 
pores slightly diverge from each other, and continue apart until 
they approach the api al disc ; the distance between the rows a, 
pores in this species is less than in any other Nucleolite of the 
same size we know, and forms one of the characters by which it 
is distinguished from its congeners ; the ambulacral areas are 
likewise slightly elevated above the general surface of the test in 
