644 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxii. 



dd. Skill more pliable, with many wheels. Flank papilla^ small or absent. 



e. Mid ventral radius without pedicels L.etmogone. 



ee. Midventral radius with two rows of pedicels Pannychia. 



bh. Tentacles dendroid. Retractor muscles present Cucumaeiid.-r. 



c. Tentacles 20, five pairs of large alternating with five pairs of verj' much smaller 

 ones. No large scales on dorsal surface, which always has scattered pedi- 

 cels Thyonidium. 



cc. Tentacles 10; ventral surface flattened, forming a creeping sole on which 

 pedicles are arranged in two or three longitudinal bands. Dorsal surface 

 with large scale-like plates which imbricate; no dorsal pedicels. Mouth 



and anus dorsal, often guarded by large plates or valves Psolus. 



aa. No pedicels or papillae, and no respiratory trees. Tentacles arise only partly 

 from radial canals, and partly from ring canal. 



Order Paractinopoda, Synaptid/E. 

 h. Calcareous deposits in the skin consisting of anchors and perforated plates. 

 c. Anchor arms smooth, without serrations; vertex with minute knobs; anchor 

 plates symmetrical. 

 d. Handle of anchors with l)ranches; /'artilaginous ring absent, or present. 

 e. Calcareous ring without anterior projections; madreporic canal single 

 (never many); cartilaginous ring absent; handle of anchor plates with 



2 large and several small smooth holes Ei'apta. 



ee. Calcareous ring with conspicuous anterior projections; numerous madre- 

 poric bodies; cartilaginous ring soinetimes present; 2 large holes in 



handle of anchor plates absent Opheodesoma. 



dd. Cartilaginous ring present; handle of anchor without branches. 



Synaptula. 

 cc. Arms of anchor usually serrate; anchor plates asymmetrical, the circumfer- 

 ence uneven or incomplete; not narrowed into a handle; tentacles digi- 

 tate Protankyra. 



hh. Calcareous deposits never anchors and plates, but wheels with six spokes, 

 S-shaped rods, small C-shaped rods or simple rods, sometimes oval grains; 

 sometimes wanting. 



c. Deposits absent (sometimes present as oval grains) Anapta. 



cc. In addition to wheels collected in little heaps, often small curved, C-shaped, 

 or straight rods, smooth, rough, or parteil at tips; no sigmoid bodies. 



Chiridota. 

 ccc. Sigmoid rods present; sometimes also wheels, either in heaps or scattered. 



T.EXIOGYRUS. 



Order ACTINOPODA Ludwig, 1891. 

 Family HOLOTHURIID.E Ludwig. 



Iloluthnrlidif LunwiG, ]Mem. Mus. Comp. Zool., XVII, 1894, ]x 7. 



Genus ACTINOPYGA Bronn. 



MilUeria" Jager, Dissertatio de Ilolothuriis, 183.';. 



Actinopyga Bronn, Klassen u. Ordnungen des Thierreichs, 1860. 



a Notwithstanding the fac^t that MuUeria Jiiger is at least three times preoccupied 

 (Ferussac, 1823, mollusca; Desmarest, 1825, Crustacea; Fleming, 1828, echinoderma, 

 according to Agassiz's Index Universalis), some of the leading authorities still 

 employ the name, although Professor Bell pointed out the error in Ann. Nat. Hie., 

 (5) XX, p. 148. 



