40 Dr. T. Wright on new Species of Echinodermata 
all the specimens we have examined ; the interambulacral areas 
are of unequal width, the antero-lateral pair are the narrowest, 
they are however about nine times the width of the anterior 
single ambulacral area ; the postero-lateral pair are ;3,ths of an 
inch wider than the antero-laterals, and the single interam- 
bulacrum is about the same width as the latter. The anal valley 
extends from the apical disc to the posterior border; it is very 
narrow, with deep perpendicular sides above, which become shal- 
low and expanded below ; the postero-lateral interambulacra are 
swollen out at the margin; the single interambulacrum is 
considerably produced, and its posterior border is broadly trun- 
cated and slightly deflected, within which the expanded sides of 
the anal valley are excavated. The base is nearly flat, the eleva- 
tions are due to the prominence of the postero-lateral interam- 
bulacra, and to the deflection of the smgle interambulacrum. 
The mouth is excentral, nearer the anterior margin, and the oral 
lobes are small; the apical disc was of moderate size, judging 
from the space it occupied, but it is absent in all our specimens ; 
the surface of the test was covered with very minute tubercles, 
which in the examples before us are nearly all effaced. 
Affinities and differences.—N. Michelini in its oblong form, 
truncated posterior margin, and narrow anal valley resembles 
N. Solodurinus, but it is readily distinguished from it by the 
form, narrowness, and structure of the ambulacral areas; in 
N. Solodurinus they are expanded and petaloid, and in N. Miche- 
lint they are narrow and lanceolate ; the pores at no point are 
at any great distance apart; the anal valley in both species ex- 
tends from the apical disc to the margin, but it is more expanded 
below and deeper above in N. Michelini than in N. Solodu- 
rinus. We have before us Clypeus angustiporus, Agass., from 
a coarse Oolitic rock (Bradfordien?) near Metz, collected by 
M. Terquem, and kindly sent us by M. de Loriére; from this 
species N. Michelini differs in many particulars; in the French 
Urchin the apical disc is excentral, the anal valley is wide above 
and not much expanded below, the ambulacral areas are narrow, 
and the test gradually declines from the vertex to the anterior 
border, which forms a rather acute angle ; the base is undulated, 
and the mouth-opening is nearly central ; these characters clearly 
distinguish our Urchin from it. N. Michelini differs so widely 
from all the various varieties of N. sinuatus with which we are ae- 
quainted, that it cannot possibly be mistaken for either of them, 
if any care be taken when a comparison is made between them. 
Locality and stratigraphical range.—We have collected this 
species only from the Freestone beds of the Inferior Oolite of 
Wallsquarry and Nailsworth ; the specimen figured was cut out 
of the centre of a block of building stone ; the oolitic grains are 
