22 Dr. T. Wright on new Species of Echinodermata 
name Acrosalenia rarispina, giving the Great Oolite of Minchin- 
hampton for its locality. As that gentleman has kindly favoured 
us with pen-and-ink sketches of the species described as new in 
that paper, we have no difficulty in deciding on the identity of 
his specimen. Moreover we have ascertained the collection from 
whence it originally came. The error committed by this learned 
author in the genus must have arisen from the disc in his spe- 
cimen having been covered with “adhering siliceous matrix,” 
and from his having overlooked the very remarkable character 
pointed out by Agassiz, “les tubercules trés espacés.” We have 
been fortunate to receive a typical specimen of the original spe- 
cies from the Great Oolite of Langrune, through the kindness 
of our friend Professor Deslongchamps ; we have compared the 
French Urchin with specimens obtained from the same locality 
as that from whence Prof. M‘Coy’s was collected, and there is not 
a shadow of a doubt about their perfect identity. We have 
figured in detail this beautiful and singular form, to prevent the 
possibility of mistakes occurring about it in future. 
This pretty little Hemicidaris is very distinct from all others of 
the group to which it belongs: the test is nearly hemispherical, 
and the few primary tubercles stand prominently at great di- 
stances apart from the surface of the test. The narrow ambulacral 
areas are slightly flexuous above, and have from four to six large 
perforated tubercles at their base only, the sides and upper part 
of the areas having first four, and then two rows of small imper- 
forate granules upon their surface about equal in size to the gra- 
nulation which covers other parts of the test. The poriferous 
avenues are cepressed, and the pedal pores are disposed in pairs 
throughout. The interambulacral areas depart considerably from 
the typical structure of this portion of the test in other Echinide ; 
they are three times the width of the ambulacra, and have at 
their base three large primary tubercles, two on one side and one 
on the other, with a smaller tubercle above the single large one ; 
on the sides and upper part of the areas there are only three 
primary tubercles, two on one side and one on the other, making 
only three pairs of primary tubercles in the interambulacral areas, 
those of the base being closely set together, and those on the 
sides at great distances apart ; the tubercles are large and hemi- 
spherical and only slightly perforated ; the mammillary eminences 
which support them are small and ring-like with faintly marked 
crenulations, and the areolas are rather wide and only slightly 
grooved, so that the tubercles project prominently and abruptly 
from the surface of the test. The margin of the areolas is en- 
circled by a row of granules rather larger than those which cover 
the rest of the intertubercular surface of the plates; here the 
granules are close-set and disposed without much regularity. 
