from the Island of Malta. 93 
Malta so well exhibits the distribution of the various beds with 
their faults and denudation. a tee 
Brissopsis crescenticus (Wright, n. sp.). Pl. VI. fig. 2 a-c. 
Test oblong, rounded before and truncated behind ; flattened on 
the dorsal surface, and deeply indented by the ambulacral 
areas; the ambulacrum forms an anteal sulcus; the anterior 
and posterior ambulacra on each side form two lateral crescents 
that abut at the longitudinal line; the antero-lateral pair are 
the longest and widest, they curve forwards and backwards, 
and the posterior pair curve backwards and forwards; the 
anterior pair form an angle of 45°, the posterior pair an angle 
of 65°; the apical dise lies in a depression formed by the 
confluence of the apices of all the ambulacra ; the posterior 
border is squarely truncated, with the anal opening in its 
upper angle ; the base is convex, with few tubercles and wide 
naked spaces formed by the basal portions of the ambulacra ; 
the mouth is situated in the anterior third. 
Dimensions.—Antero-posterior diameter 1,5 inch, transverse 
diameter 1,4; inch, height {ths of an inch. 
Description.—The most remarkable feature in this species 
consists in the mode of arrangement of the ambulacra ; the ante- 
rior and posterior areas of each side curve in opposite directions 
and form crescents, the convexities of which are directed towards 
the middle line of the test, and give value to the name proposed. 
The antero-lateral pair form an angle of 45°; they are about 
the same length as the posterior pair, but are a little broader 
and are more divergent : there are nineteen pairs of holes in the 
external zone, and fourteen in the inner; the posterior pair 
are nearly parallel with each other, and have a slight curve for- 
wards to form the posterior horn of the crescent; they are not 
so much developed as the anterior pair; the external zone of 
holes contains fifteen pairs, but the inner zone (2c) is imperfectly 
developed, from their close approximation to those of the oppo- 
site area: the apical disc is small ; the four genital holes are 
large, the anterior pair being more closely approximated than the 
posterior pair ; it 1s situated nearer the anterior than the posterior 
border and lies in a confluent depression, in which the apices of all 
the areas freely converge. The single ambulacrum is rather longer, 
but not so wide as the anterior pair ; its lateral row of single holes, 
with their accompanying tubercles, are small and indistinctly 
seen, and it forms an inconsiderable anteal sulcus : the posterior 
border is squarely and obliquely truncated, and in its upper part 
near the dorsal surface is the large anal opening: the base is 
rather convex; the sternal portion of the single interambu- 
