ASTHENOSOMA. 143 



1. ASTHENOSOMA. 



Asthenosoma, Gritbe, JB. schles. Ges. xlv. (1868) p. 42 ; A. Ay. Rev. 



Ech. (1872) p. 272 ; Ludwiy, Zeitsch. f. wiss. Zool. xxxiv. (1880) p. 70 ; 



Duncan, J. Linn. Soc. xxiii. (1889) p. 43. 

 Calveria, Wyv. Thorns. Phil. Trans, clxiv. (1874) p. 737. 



An Echinothurid in which the imbrication of the coronal plates 

 is very marked, and the ambnlacral 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 

 coelom 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. Thorns. Proc. Roy. Soc. Lond. xx. (1872) 



p. 494 ; Phil. Trans, clxiv. (1874) p. 738 (non Proc. Roy. Soc. xyiii. 



(1869) p. 445), pis. lxiv. & lxv. 

 Asthenosoma hystrix, A. Ay. Rev. Ech. (1872) pp. 93 & 273, pi. ii. 



figs. 1-5; id. Bull. Mm. C. Z. viii. (1880) p. 74; id. Mem. C. Z. x. 



(1H83 X p. 29, pis. xiii. & xiv. ; Rathbun, Proc. U.S. Nat. Mus. ix. 



(1886) p. 267 ; Bell, Proc. Roy. Dubl. Soc. vii. (1892) p. 526, 



pis. xxiv. it xxv. 

 Asthenosoma reynoldsii, A. Ay. t. c. (1880) p. 75. 

 Calveria leuestrata, 11'yo. Thorns. Phil. Trans, clxiv. (1874) p. 741, 



pi. lxiii. figs. 9 & 9 a, & pis. lxvi. & lxvii. 

 Asthenosoma fenestratum, A. Ay. 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. 



