104 Dr. T. Wright on Fossil Echinoderms 
basal portions of the lateral and anterior pairs slope gently 
towards it; the tracks of the ambulacra are nearly naked as they 
approach the mouth, and are here perforated with buccal pores. 
The mouth is at the anterior third, and has a projecting under- 
lip; the tubercles on the upper surface are small and of a 
uniform size; those on the sternum are larger, and are per- 
forated and set on crenulated summits; they are arranged in 
lines radiating from a posteal point ; the tubercles of the inter- 
ambulacral pairs are the largest. 
Affinities and differences.—This species very much resembles 
the living S. canaliferus, but it may be distinguished from it by 
the following characters :—S. eurynotus is broader and more 
depressed before, and is not proportionally so high behind as 
S. canaliferus ; the antero-lateral ambulacra are more divergent, 
and the postero-lateral pair are proportionally longer in S. eury- 
notus than in S. canaliferus. The single ambulacrum is about 
the same depth as the pairs, and has the pores in a single file in 
S. eurynotus, whereas in S. canaliferus this area is much deeper, 
and the pores are not in single file, but are crowded together, so 
that they form three rows in a part of the zone; the tubercles 
of the base are much larger in the living than in the fossil 
species. S. ewrynotus is distinguished from S. Parkinson by 
its f-shaped ambulacra being less divergent, and the position of 
the apical disc, which is much nearer the posterior border in S. 
eurynotus ; the anterior ambulacrum is likewise much wider and 
deeper in that Urchin than in S. Parkinsoni: the great develop- 
ment of the single interambulacrum, and breadth of the pos- 
terior border in S. Desori sufficiently mark that species as 
widely distinct from S. eurynotus. 
Locality and position.—Collected in bed No. 4, the calcareous 
sandstone at Malta ; we have it also from Santa Manza, Corsica, 
sent us by M. Michelin; it has likewise been found in the Ter. 
moyen de Perpignan, Cagliari. 
Schizaster Desori, Wright, n.sp. Pl. VI. fig. 3 a—c. | 
Test cordate, broad and much depressed before, narrow and 
much elevated behind ; ambulacral areas long, straight, and 
very divergent ; peripetal fasciole forms an acute angle on the 
anterior interambulacra; apical disc situated at the posterior 
third of the dorsum; angle of the antero-lateral ambulacra 
44°; angle of the postero-lateral pair 60° ; posterior border 
truncated obliquely downwards and inwards; sternal portion 
of the interambulacrum tumid and prominent at the base, 
amounting almost to a deformity. 
Dimensions.—Antero-posterior diameter 2 8, inches, transverse 
diameter 247, inches, height at the deepest part 14%, inch. 
