106 Dr. T. Wright on Fossil Echinoderms 
the anus, and meets the one from the opposite side, at the 
middle line near the base ; in the triangle thus formed, the caudal 
process and anus occupy the base, and a depression lies beneath 
which is filled with tubercles somewhat larger than those on the 
dorsum, but smaller than those on the base; the tubercles are 
perforated and raised on prominent crenulated bosses (fig. 3 ¢) ; 
the sternal and basal portions of the test, as well as the anterior 
border, being furnished with much larger tubercles. 
Affinities and differences.—The straightness of the pairs of 
ambulacra, and the narrowness of the single anterior ambulacrum, 
are alone sufficient to distinguish S. Desori from S. eurynotus 
when viewed only from above, but when we add to these the 
remarkable oblique truncation of the posterior border (fig. 3 5), 
the great tumidity of the sternum, and the sloping character of 
the sides of the base, we discover how widely different these two 
forms are from each other. The same group of characters serves 
to distinguish it from S. Parkinsoni, but in this species the apical 
disc is much nearer the centre of the test; the antero-lateral 
ambulacra are arched outwards, and the postero-laterals are pro- 
portionately longer. 
Locality and stratigraphical position.—Collected from the cal- 
careous sandstone bed No. 4, at Malta; the large specimen be- 
longs to the Bristol Institution, the others form part of Earl 
Ducie’s collection. We dedicate this species to M. Desor of 
Neufchatel, one of the learned authors of the ‘Catalogue raisonné 
des Echinides.’ . 
Schizaster Parkinsoni, Defrance sp. PI. V. fig. 3 a-c. 
Syn. Spatangus Parkinsoni, Defrance, Dict. Sc. Nat. tom. 50. p. 96 ; 
Desmoulins, Etudes sur les Echinides, p. 394. no. 29. 
Spatangus lacunosus, Parkinson, Organic Remains, vol. ii. tab. 3. 
fig. 12. 
ee Parkinsoni, Agassiz and Desor, Cat. raisonné, Ann, Se. Nat. 
tom. vill. p. 22. 
Test cordate, depressed anteriorly, elevated posteriorly ; apical 
dise nearly central ; sides expanded and tumid ; cheeks sloping 
and contracted ; single ambulacrum rather wider than the 
anterior pair, of the same diameter throughout, except near 
the apex; antero-lateral ambulacra diverge at an angle of 35° ; 
length 1 inch ; postero-lateral make an angle of 65°; length 
;6;ths of an inch ; posterior part of the back raised into a long 
prominent carina; posterior border obliquely truncated ; base 
convex ; mouth near the anterior border ; anteal sulcus nar- 
row and of moderate depth. 
Dimensions. — Adult. Antero-posterior diameter 233 inches, 
transverse diameter 234 inches, height 143 inch, 
