from the Island of Malta. 103 
Schizaster eurynotus, Sismonda, Mem. Echin. Foss. Nizza, tab. 2. 
fig. 3. p. 31; Agassiz and Desor, Ann. Sc. Nat. tom. viii. p. 21. 
série 3. 
Spatangus Scilla, Desmoulins, Etudes sur les Echin. no. 24. p. 392. 
Test heart-shaped, depressed and rounded anteriorly, elevated 
and pointed posteriorly ; ambulacral areas deeply excavated ; 
the single ambulacrum long, deep, wider in the middle and 
narrower at the anterior border, which is deeply grooved 
by it: antero-laterals slightly f-shaped ; angle 52°; length 
1,5, inch: postero-laterals, angle 72°, short, ths of an inch ; 
apical dise with two genital holes near the posterior third ; 
single interambulacrum elevated into a prominent carina ter- 
_ Ininating in a caudal hooked process. 
Description.—This Urchin resembles Schizaster canaliferus 
now living on the shores of the Mediterranean, and for which it 
has been mistaken by some naturalists, but an attentive study of 
the living and fossil species discloses characters by which they 
may be distinguished from each other. The test in S. eurynotus” 
is cordate, depressed before and elevated behind. The ambu- 
lacral areas are deeply depressed; the odd or anterior ambu- 
lacrum is nearly twice the width of the pairs, it swells out in the 
middle, is blunted at the apex, and most contracted at the 
anteal suleus, which is deep and narrow when contrasted with 
the width it attains above. The poriferous zones lie at the base 
of the walls of the sulcus; the very narrow plates that compose 
the floor of this area are each studded with a row of small gra- 
nules. The antero-lateral ambulacra diverge at an angle of 52°; 
they are slightly f-shaped, and are 1,5, inch in length: the 
numbers of holes in the zones are thirty-six and thirty-four. 
The postero-lateral pair are short, and make an angle of 72°; 
they are ;%,ths of an inch in length, and have respectively 
twenty-six and twenty-four holes in their zones. The peripetal 
fasciole passes close to the base of the posterior pair, dips slightly 
into the space which separates the anterior from the posterior 
pair, runs at some distance from the anterior pair, passes close 
by the base thereof obliquely towards the anteal sulcus, into 
which it dips, and meets its fellow from the opposite side: the 
very narrow postero-lateral fasciole is directed obliquely down- 
wards and backwards, and unites with its fellow at some distance 
below the anus. The test is depressed anteriorly and sloped 
away at the checks, whilst behind it is much elevated. The 
interambulacrum forms an elevated ridge between the posterior 
ambulacral pair, and is produced into a caudal-like process 
behind, beneath which the circular anus is pierced ; the sternal 
portion of the odd interambulacrum is tumid and convex ; the 
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