SCHIZASTER. 163 
between irregularly hexagonal plates, in double series, from the apex 
to the mouth. The ambulacral aree widen somewhat from the 
apex to the ambitus, and become slightly narrower from the ambitus 
towards the mouth; they are about 4 millims. in width at the 
widest point, the lateral ambulacral spaces being 12 millims. 
At the mouth the ambulacra expand into a very distinct floscelle, 
and the interambulacral are end in bourrelets crowded with 
tubercles and bearing combs of long spatulate spines. The plates 
of the apical disk are so compacted and fused together, that it is 
difficult to trace their outline. Eight holes, nearly of equal size, 
surround a central madreporic tubercle ; of these, five terminate the 
ambulacra, and are the pits for the sense-organs, the other three are 
ovarial. The posterior and the right anterior ovaries and ducts are 
undeveloped. 
“The surface of the test is crowded with minute tubercles for the 
articulation of the larger spines and many small granules. The 
tubercles are imperforate, with a smooth mammillary boss ; they 
are placed in circular scrobicular depressions, but they project some- 
what above these and above the surface of the test. The larger 
spines, articulated to the tubercles, are cylindrical, fenestrated, with 
slight asperities on the longitudinal calcareous shafts. The small 
spines which, attached to the minute granules, form a close under- 
felting all over the test are fenestrated and slightly roughened, and 
expand at the end into a rosette of pointed tubercles. The pedi- 
cellarize articulated to some of the granules are three-valved ; they 
are very small and of a somewhat peculiar form, though resembling 
generally the smallest pedicellaria in Hchinus. 
“The bases of the valves are wider, the valves themselves are 
rounder and more arched and toothed round the edge. Round the 
mouth there are groups of three and four very small pedicellaria, 
differing in form somewhat. from the others, and with the bases of 
the valves apparently fused together.” 
I have not been able to trace this specimen, the account of which 
as here given, is copied from Sir Wyville Thomson’s description in 
the ‘ Philosophical Transactions.’ 
The species has been found at various depths between 100 and 
229 fms. off the coasts of Florida. 
2. SCHIZASTER. 
Echinus (pars), Linn. Syst. Nat. x. (1758) p. 663. 
Spatangus (pars), Lamk. An. s. Vert. iii. (1816) p. 27. 
Ova, Gray, Ann. Phil. x. (1825) p. 431. 
Micraster (pars), Ag. Mém. Soc. Neuch. i. (1836) p. 184. 
Schizaster, zd. t. c. p. 185; td. § Des. Ann, Sci. Nat. viii. (1847) p. 20; 
Al. Ag. Rev. Ech. (1872) pp. 157 & 363; Carus, Prod. Faun. 
Medit. (1884) p. 104; Duncan, J. Linn. Soc. xxiii. (1889) p. 254, 
Periaster (pars), D’ Orb. Pal. Frang. vi. (1854) p. 269. 
Test thin, generally longer than wide, highest posteriorly ; the 
paired ambulacra sunken, and the anterior longer than the posterior, 
the median in a deep groove ; two or three genital pores. 
mM 2 
