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THE VOYAGE OF H.M.S. CHALLENGER. 
SURVEY OF THE GENERA AND SPECIES, HITHERTO KNOWN, 
BELONGING TO THE ASPIDOCHIROT^. 
Family V. Aspidochirotai. 
Body with mouth and anus at opposite poles. Tentacles peltate, twenty to thirty, 
seldom eighteen. Ambulacral appendages — ^pedicels alone, or pedicels together 
with papillae, or papillae alone ; the papillae often situated on the top of warts 
or more or less prominent processes. Retractors absent. Calcareous ring of ten 
pieces, regularly devoid of posterior prolongations ; the radial pieces incised 
anteriorly, but not pierced. The left respiratory-tree generally in communication 
with the pseudhaemal vessels. 
Genus 1. Labidodemas, Selenka, 1867. 
Tentacles twenty. Ambulacral appendages — pedicels alone (1), arranged in double 
rows along each ambulacrum. Interambulacra naked. The single genital bundle 
situated on the left side of the dorsal mesentery. Anus devoid of teeth. 
C-shaped deposits present or absent. 
Not having had the opportunity of examining any representative of this genus, I am 
by no means sure of the exactness of the above diagnosis. Both Selenka and 
Semper speak of pedicels, and do not mention anything about papillae. The 
reason I have some doubts on the nature of the ambulacral appendages, is that 
Selenka points out that the ventral pedicels alone are provided with terminal 
plates, and, above all, because Ludwig speaks of dorsal “ papillae.” So far as 
I can see, the only character distinguishing the genus Labidodemas from the 
genus Holothuria is to be found in the arrangement of the pedicels, and it may 
be questionable whether this is satisfactory. 
Labidodemas semperianum, Selenka, 1867. 
Deposits — tables with the spire formed by five rods and terminating in ten teeth ; 
smooth buttons; and numerous rods or C-shaped bodies. 
Habitat . — Sandwich Islands (Selenka). 
Labidodemas selenkianum, Semper, 1868. 
Habitat . — Fiji Islands (Semper). 
On comparing the descriptions of Semper and Selenka, it is nearly impossible 
to discover any differences between this species and the preceding. The 
