ASTHENOSOMA. 143 
1. ASTHENOSOMA. 
Asthenosoma, Grube, JB. schles. Ges. xly. (1868) p. 42; A. Ag. Rev. 
Ech, (1872) p. 272; Ludwig, Zeitsch. f. wiss. Zool. xxxiv. (1880) p. 70 ; 
Duncan, J. Linn, Soe. xxiii. (1889) p. 45. 
Calveria, Wyv. Thoms. Phil. Trans. elxiv. (1874) p. 737. 
An Echinothurid in which the imbrication of the coronal plates 
is very marked, and the ambulacral plates very wide ; the tubercles 
that bear the primary spines form prominent bosses. The calca- 
reous deposit in the coronal plates may be greatly reduced, and the 
celom is divided into separate chambers by vertically disposed 
muscular bands. The organs of Stewart appear, in some species, 
to be well developed. 
1. Asthenosoma hystrix. 
Calveria hystrix, Wyv. Thoms. Proc. Roy. Soc. Lond. xx. (1872) 
p. 494; Phil. Trans. clxiv. (1874) p. 738 (non Proc. Roy. Soc. xviii. 
(1869) p. 445), pls. lxiv. & Ixv. 
Asthenosoma hystrix, A. Ag. Rev. Ech. (1872) pp. 93 & 273, pl. ii. 
figs. 1-5; td. Bull. Mus. C. Z. viii. (1880) p. 74; td. Mem. C. Z. x. 
(1885) p. 29, pls. xiii. & xiv.; Rathbun, Proc. U.S. Nat. Mus. ix. 
(1886) p. 267; Bell, Proc. Roy. Dubl. Soc. vii. (1892) p. 526, 
pls. xxiv. & xxv. 
Asthenosoma reynoldsii, A. Ag. t. ec. (1880) p. 75. 
Calveria fenestrata, Wyv. Thoms. Phil. Trans. clxiv. (1874) p. 741, 
pl. xiii. figs. 9 & 9a, & pls. Ixvi. & Ixvii. 
Asthenosoma fenestratum, A. Ag. Rev. Ech. (1872) p. 210. 
Varying considerably in one of the chief characters that dis- 
tinguish the genus—the extent to which the plates of the corona 
are calcified, so that the membranous interspaces may be very 
marked or nearly obsolete ; varying also in the size of the genital 
pores, but this perhaps is sexual. Varying from pale grey to brilliant 
pink; the bands or patches of colour varying considerably in in- 
tensity. In each interambulacrum a row of primary tubercles is 
well developed ; these diminish in size from the ambitus towards 
the mouth and are set very regularly on every plate; above the 
ambitus they are not always present on every successive plate, and 
they cease about eight plates from the apical area; in addition there 
may be a few scattered primary tubercles ; there are no prominent 
tubercles in the ambulacra. Both ambulacral and interambulacral 
plates are low from above downwards. The anal plates are very 
numerous, and nearly all bear a distinct tubercle. The madreporite 
is irregularly triangular and somewhat variable in size. The peri- 
stomial plates are thickly covered with tubercles. None of the 
spines are long, and all but the primaries are delicate and almost 
silky. 
The diameter of the test may be as much as 200 mm.; one 
measuring 110 mm. across has been extended as much as possible, 
and its vertical axis was found to measure 50 mm. Specimens in 
all kinds of distension, and, if dried, of distortion, may be observed. 
