THE APODOUS HOl.OTHUKIANS 113 



CHIRIDOTA Eschscholtz, 1829. 



Dactyloia Brandt, 1835. 

 Liosoma Brandt, 1835. 

 Trocliinus Ayres, 1852. 

 Lioderma Bronn, 1860. 



Tentacles 12, exceptionally 13 or even 14. Digits 3-10 on each side, the ter- 

 minal pair the longest. (Although Semper, Lampert, and others speak of a ter- 

 minal unpaired digit, it is very doubtful whether such normally occurs. The 

 number of digits on a tentacle may be odd, but examination will show that this 

 is due to an extra digit on one side at the base of the series.) Polian vessels 

 numerous, 3-20. No gustatory organs are known to occur. Ciliated funnels 

 usually single, sometimes collected into little groups, but not forming true 

 stalked clusters. Calcareous deposits in the form of 6-spoked wheels (Plate 

 VII, figs. 8, 15, 26) collected in little papilla- containing 10-80 of divers sizes 

 (Plate VII, fig. 24) ; no sigmoid deposits, but small curved rods with enlarged 

 ends are often present (Plate VII, figs. 16, 27), and minute oval miliary gran- 

 ules, or somewhat larger rod-shaped particles, frequently occur in connection 

 with the longitudinal muscles. 



The species of this genus are of small or moderate size and of variable 

 color. They are widely distributed in both warm and cold seas, but no one 

 species, except perhaps Icevis, has a very extensive range, so far as our present 

 knowledge shows. They occur chiefly in shallow water, often along shore, but 

 are frequently met with at depths of 500-1,000 m. and sometimes down to 3,000- 

 3,200 m. Specific differences are very difficult to determine satisfactorily, for 

 the number and length of digits on tiie tentacles is closely correlated with age 

 and size, while the number and arrangement of wheel-papillae appear to show 

 a similar correlation. Thus full-grown specimens of rotifera have the wheel- 

 papills very numerous all over the body and the ventral surface is not distin- 

 guishable from the dorsal ; but in young specimens, 20-40 mm. long, the wheel- 

 papilla' of the ventral side are few and confined to a single series in each inter- 

 radius, and such specimens therefore closely resemble rigida (Plate II, fig. 3). 

 The presence or absence of miliary granules along the radii seems to be another 

 variable feature, for Ludwig ('98b) has shown that in some specimens of 

 pisanii these granules are abundant, in others infrequent, and in still others 

 entirely wanting. In the light of these facts, it is not strange that the num- 

 ber of species in the genus and their geographical distribution are still uncer- 

 tain. The species described by Miiller ('50) as pygmrea is apparently a young 

 IcBvis or possibly rotifera (Selenka ('67) says it is West Indian), while the form 

 called rubeola by Quoy and Gaimard ('33) is absolutely unidentifiable at pres- 

 ent, and it may not be one of the Chiridotinae at all. The same is true of 

 Synapfa coriacen Agassiz ('52), which has been considered a synonym of 

 Chiridofa lavis. The holothuriau called AspidocJiir mertensi by Brandt ('35) 

 is thought by Ludwig ( '81&) to be a Chiridota. 

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