NO. 3592 LISSOTHURIA — PAWSON 5 



sharp points on free edges. Arrangement of valves indeterminable. 

 Dorsal surface completely covered by imbricating scales, through and 

 between which pass inconspicuous tube feet. Finely papillate 

 integument containing calcareous deposits overlies scales. Sole 

 elongate, oval, fringed by 5-6 rows of closely crowded tube feet, 

 which form a continuous margin. Midventral radius with 3-5 rows 

 of tube feet throughout. Sole leathery, opaque. Tentacles richly 

 branched. Color in alcohol yellowish white overall. 



Calcareous deposits of dorsal surface (apart from scales) are towers, 

 hourglass-shaped deposits, and some flat plates. Towers complex, 

 height ranging from 0.25 to 0.40 mm, diameter at base 0.15 to 0.20 mm. 

 Tops of towers irregular, not carrying distinct teeth (fig. If). Hour- 

 glass deposits fragile, with numerous perforations, varying greatly in 

 size and shape; length ranges from 0.08 to 0.15 mm (fig. 1b). Flat 

 plates with larger central perforations and smaller marginal perfora- 

 tions present; diameter ranges from 0.05 to 0.3 mm (figs. 1d,e). 

 Plates fragile, often broken. 



Sole with flat perforated plates of varying shape (fig. Ic), greatest 

 length 0.17 to 0.22 mm. Margins of plates smoothly indented; some 

 plates with low rounded knobs. 



Tentacles ^\ith minute rosettes that vary greatly in size and degree 

 of complexity (fig. 1g), also curved or flat perforated plates and rods 

 (fig. 1a). Tube feet with end plates; feet supported by narrow per- 

 forated rods of average length 0.19 mm (fig. 1h). 



Color. — ^\^errill (1867, p. 322) noted that the color in alcohol of this 

 specimen was "light purple, whitish beneath, disk [sole] purple, with 

 a yeUowish white ring around the mouth; tentacles purple at base, 

 the subdivisions yellowish." At the time Verrill described the 

 specimen, it had been in alcohol for less than six months, and thus 

 apparently the color had faded very little. No trace of this striking 

 original coloration now can be found. 



HoLOTYPE. — Peabody Museum of Natural History, Yale Uni- 

 versity, YPM no. 5327. 



Type-locality. — Pearl Island Panama; coUected by F. H. Bradley, 

 December 1866. 



Additional material. — A collection of six specimens from Taboga, 

 Panama, was examined in the Zoological Museum, Copenhagen. 

 Some information on the internal anatomy of the species is given below. 



Total length 27-37 mm. Midventral radius with 3-5 rows 

 of tube feet anteriorly and posteriorly, but at center of radius 

 rows, without exception, double. Dorsal surface of body with 8-10 

 scales between oral and anal apertures. Mesentery of posterior 

 loop of intestine lies in left ventral interradius. Gonad a large mass of 

 long unbranched cacea. A single bulbous Polian vesicle; respiratory 



