108 Dr. T. Wright on Fossil Echinoderms 
the sides by the fasciole, and above by the anal opening and 
caudal process ; the base is convex ; the sternum is not very pro- 
minent, and has lines of tubercles proceeding in radii from a 
point near the border ; the basal portions of the posterior ambu- 
lacra are naked, and around the mouth buccal pores are seen, 
which extend at considerable intervals along the trajet of the 
posterior pair. The mouth is situated in the anterior fourth of 
the base and has a projecting under-lip; the basal parts of the 
interambulacra glide mto the general convexity of the floor of 
the test; the lateral pair have a regular tuberculation, but on 
the anterior pair the tubercles are larger and more irregular. 
Affinities and differences.—The nearly central position of the 
apical disc and the greater divergence of the antero-lateral am- 
bulacra distinguish this Urchin from its congeners ; the narrow- 
ness of the odd ambulacrum and the absence of the swelling-out 
im the centre of the same, serve to separate it from S. eurynotus ; 
the blunt caudal process, the small posterior border, and the 
general tumidity of the sides distinguish it from S. Desori. 
Locality and stratigraphical position.—Collected from bed 
No. 4, the calcareous sandstone at Malta, where it is common ; 
it is found likewise in the Molasse, middle tertiaries, of Mar- 
tigues, Bouches-du-Rhone. Fine specimens are contained in the 
British Museum, Jermyn Street Muscum, and that of the Bristol 
Institution. 
Since the preceding sheets of this memoir have been passing 
through the press, we have had the opportunity of examining 
the Maltese fossils belonging to the Geological Society, and some 
that had escaped our notice in the British Museum collection ; 
from these new materials the followmg notes are now added :— 
Clypeaster Reidiz, Wright, n. sp. 
Test large, broadly pentagonal, and much elevated; border 
- abrupt, margin thin and undulated, rising with steep sides at 
angles of 60°, and with a very little curve towards the vertex, 
which is nearly central; petaloidal portions of the ambulacral 
areas large, nearly equal in width, and extending over nearly 
three-fourths of the sides ; base quite flat; mouth small, pen- 
tagonal, nearly central; basal ambulacral sulci proceeding 
from the angles of the mouth, narrow, and sharply defined ; 
anus round, near the posterior margin ; tubercles on the upper 
surface small and closely set together, those on the base a 
little larger; apical dise nearly central and prominent, with 
an outer circle of genital holes, and an inner circle of eye- 
holes having the madreporiform tubercle in the centre. 
