674 PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXXII. 



zontal), but sometimes fewer, rarely more. The large tables are very 

 scarce, and the tips of the few seen appeared to have been l^roken. 

 The form is best shown by the tig-urc. The disk is perforated with 

 several tiers of holes and has no well-defined rim, being irregular from 

 imperfectly inclosed perforations. The spire is about 0.12 mm. in 

 height (relatively too small in drawing) and has two or three cross- 

 beams. Apparently it ends in a single point. The buttons differ much 

 in size. While a very few are smooth, the vast majorit}^ are irregu- 

 larly beset with small protuberances, and the edge is minutely incised. 

 Common forms are figured. The average length varies from about 

 0.06 to 0.00 mm., but buttons 0.135 mm. or even larger are present in 

 the ambulacral appendages. An average button of the dorsal peri- 

 some measures 0.056 mm., but in buttons of this size the number of 

 irregular holes varies from one to eight. Frecjuently asymmetry 

 characterizes the number and position. The supporting rods of 

 pedicels and papillae are curved, robust, smooth, with a spiny or scal- 

 loped border. The middle is expanded and perforated on either side 

 of the central shaft and the tips are slightly expanded also, commonl}- 

 minutely perforated. In the pedicels the rods frequently have onl}- 

 lateral processes at the sides, with denticulate ends. These processes, 

 by joining at the tips, form perforations. At base of pedicels and 

 papillae large rods or buttons of intermediate form are found, rather 

 more sparsely knobbed than the regular buttons. They resemble the 

 largest buttons rather more than rods. AY hen the little protuberances 

 begin to appear on the rods, it is at the edges. Pedicels have large 

 terminal plates; the papilla^ small rudimentary ones. 



This species is apparently quite unique. At least there are no close 

 relatives. 



Genus LABIDODEM AS Selenka. 



Labidodemas Sklenka, Beitrilge zur Anatomie u. .Sys^tematik der Holothnrien, 

 Zeitsch. f. wiss. Zool., XVII, 1867, p. 309. Type, L. semperianurii. 



Tentacles 20. Ambulacral appendages, ])edicels and papilla?, the 

 former in a double ^ej-ies along each of the three ventral radii, the 

 latter in a double series along two dorsal radii, or pedicels alone. 

 Interambulacra naked. Single genital bundle on left side of dorsal 

 mesentery. C-shaped deposits. All deposits absent in one species. 

 No anal teeth. The C-shaped deposits unlike those of Stichopus. 

 Genus differs from Ilolothiiria in arrangement of pedicels and papilhe. 



* LABIDODEMAS SEMPERIANUM Selenka. 

 Labklodanas semperkinum Selenka, Beitrage, p. o()!t, j)!. xvii, figs. 1-3. 



Tentacles 20, very small; pedicels in three ventral double series; 

 papilla} in two dorsal double series. Deposits: Tables, buttons, and 

 C-shaped bodies. Tables with a spire made up of ffve rods, one cross- 



