80 Dr. T. Wright on Fossil Echinoderms 
ceolate at their upper fifth: the poriferous avenues are very nar- 
row, and extend three-fourths of the distance between the apex 
and the border : the pores in the avenues are only about one line 
apart, and are united by short slits directed obliquely upwards 
and inwards at nearly equal spaces apart from the base to the 
apex ; the pores in the outer and inner series in each zone are 
about the same size throughout : the narrowness of the poriferous 
avenues forms a very important character in this species, by 
which it is distinguished from an allied form, C.conoideus. The 
interambulacra are of a triangular form ; the antero-lateral are the 
smallest, and the postero-lateral and single interambulacrum of 
about the same size are the largest: the apical disc is small, and 
situated nearer the anterior than the posterior border, which 
occasions a slight difference between the angle of inclination of 
the anterior and posterior sides of the test: the centre of the 
disc is occupied by a prominent button-like spongy madrepo- 
riform body, around which the genital and ocular plates are 
arranged, but their lines of suture can only be distinguished in 
weathered specimens, or by removing the superficial layer of the 
plates. The entire surface of both areas is covered with tuber- 
cles, very much alike both as regards size, form, and irregularity 
of arrangement ; the only parts exempt from tubercles are the 
interporiferous septas of the avenues: the base is concave: the 
mouth is situated in the centre of the disc, and is surrounded 
by five large prominent lobes: the ambulacra form petaloid 
depressions between the oral lobes, in which a number of pores 
are clustered together in pairs. The anus is a large, transversely 
oblong opening, placed immediately beneath the posterior mar- 
gin ; from it to the mouth an elevated ridge of the test runs : the 
single interambulacrum is slightly produced posteriorly where 
the anus teminates: the tubercles are larger, and placed at 
greater intervals apart on the base than on the dorsal surface : 
the marginal fold of the test forms an acute angle, and on the 
border thereof the tubercles are clustered closer together in 
greater numbers, with smaller interspaces between them, than in 
any other part of the skeleton. 
Affinities and differences.—This species very much resembles 
in form and size C. conoideus, but it is readily distinguished from 
it by the following characters : the ambulacral areas are smaller, 
the poriferous zones are narrower, and the outer and inner pores 
of each pair are nearly of the same size, whilst the septas between 
the pores are thicker; the dorsal surface is not so much ele- 
vated, the base is concave, the anus is large and transversely 
oblong, and the mouth possesses very prominent oral lobes. 
Locality and stratigraphical range.—This Urchin was collected 
at Malta, from bed No.2. The fine specimen before us belongs 
