18 Dr. T. Wright on new Species of Echinodermata 
The imperfect condition of the shell prevents us from ascer- 
taining the precise number of these tubercles there were in each 
row, but judging from the number (eight) contained in an im- 
perfect column, we suppose there could not have been less than 
from twelve to fourteen; they increase gradually in size from 
the mouth upwards, and are of a moderate magnitude when 
compared with the shell they adorn. The areolas are small and 
not prominent, and the tubercles are deeply perforated. The 
space between the two rows of tubercles is wide and filled with 
close-set miliary tubercles, most of which are raised on eleva- 
tions, and have their summits perforated; these all support 
small spines, which are well preserved in situ in our specimen. 
The spines are of two kinds—those articulated with the large 
tubercles (the primaries), and those articulated with the small tu- 
bercles (the secondaries). The primary spines exhibit a peculiar 
structure: the head is large, increasing gradually in diameter 
from the articulating cavity to the circular band ; the rim of the 
acetabulum is coarsely and deeply crenulated, and the raised band 
is prominent, narrow, and finely milled ; the neck tapers gradually 
from the band to the point where it joms the stem, which has the 
same structure as the head, and its surface is delicately sculp- 
tured with fine longitudinal lines; the stem is united to the 
neck by an oblique harmonia suture. The structure of this part 
of the spine differs from that of the head and neck; in the 
spines denuded of their external layer, it has a horny semi- 
transparent appearance ; in those in which this layer is pre- 
sent the surface is sculptured with longitudinal lines of micro- 
scopic delicacy, and there are numerous small processes, having 
their points directed forwards, arranged with some regularity in 
rows. The stem is circular or slightly compressed; but as 
none of the spines are complete, a part having been broken 
off, we are unable to ascertain their length. The secondary 
‘spines are very uniform in size and structure, and are abun- 
dantly preserved in situ; they measure from ths to ,>ths of 
an inch in length and are round, and have their surface orna- 
mented with fine longitudinal limes. The mouth is armed with 
a powerful dental apparatus: three of the jaws are very promi- 
nent; the external surface of each is strengthened by three pro- 
minent ridges; the teeth are large, but are fractured. As the 
under surface of the test only is shown, we are unable to describe 
the ovarial dise and the dorsal surface thereof. 
Affinities and differences—This Urchin belongs to the same 
group as C. Fowlert and C. maxima, Goldf. It resembles the 
former in the form and structure of both areas, and in the gra- 
dual development of the primary tubercles from the mouth 
upwards. It is distinguished from that species, however, by the 
