THE HOLOTHURIOIDEA 229 



small spicules. Genital tubes in a right and left tuft. Genera Psychro- 

 trephes, Theel ; Euphronides, Theel ; Psychropotes, Theel, Fig. III. 5 ; 

 Benthodyteg, Theel. SUB-FAMILY 2. DEIMATINAE. Mouth sub - ventral. 

 Papillae large and numerous. Tube-feet large, generally only on the lateral 

 ventral radii. Calcareous ring of five radial and five interradial pieces. 

 Genital tubes in a right and left tuft. Genera A. With a row of large 

 papillae above the lateral ventral podia. Median ventral podia rudimentary 

 or absent. Twenty tentacles Deima, Theel (Fig. III. 1) ; Oneirophanta, 

 Theel ; Orphnurgus, Theel ; Scotodeima, Ludwig. B. Without a distinct 

 row of lateral ventral papillae, fifteen to twenty tentacles. Wheel 

 spicules Laetmogone, Theel ; Ilyodaemon, Theel (Fig. III. 2 ; Pan- 

 nychia, Theel ; Capheira, Ludwig. SUB -FAMILY 3. ELPIDIIXAE. Mouth 

 generally sub-ventral. Papillae usually few and large. Podia only on 

 the lateral ventral radii. Calcareous ring of five radial pieces. Genital 

 tubes in one or two tufts. Genera A. With ten tentacles Parelpidia, 

 Th^el ; Elpidia, Theel (Fig. III. 6) ; Scotoplanes, Theel ; Kolga, Dan. 

 and Koren ; Irpa, Dan. and Koren ; Peniagone, Theel (Fig. III. 4) ; 

 Scotoanassa, Theel. B. With more than ten tentacles Achlyonice, 

 Theel ; Enypniastes, Theel. 



The Elpidiidae are a deep-sea group of wonderfully diverse outward 

 form. The body is generally flat or even concave ventrally ; it is often 

 produced along its lateral edge into a brim, which may be posterior (as in 

 Scotoplanes), anterior (as in Elpidia, purpurea, Thdel), both anterior and 

 posterior (as in Scotoanassa), or- all round (as in the Psychropotinae). 

 The mouth may be quite ventral, and some way behind the anterior 

 edge of the body (Fig. III. 5). The anus is terminal, dorsal, or ventral. 

 Tube-feet occur on the ventral radii only, and are often remarkable for 

 their large size and paired arrangement (Fig. III. 6), resembling the feet 

 of a segmented animal. The dorsal papillae also may be distinctly 

 paired and very large (Fig. III. 1). Peculiar posterior dorsal appendages, 

 sometimes of huge size (Fig. III. 5), are developed in Euphronides and 

 Psychropotes. Somewhat similar anterior appendages occur in Peniagone 

 (Fig. III. 4). These outgrowths of the body-wall are often supplied with 

 right and left canals from the radial, water -vascular system. The most 

 characteristic spicules are C-shaped, four-armed wheels (Fig. III. 3), 

 and perforated plates. The calcareous ring is generally but slightly 

 developed ; in the Elpidiinae the five radial pieces only are represented 

 as single-branched spicules. Auditory vesicles or otocysts are sometimes 

 situated in the Elpidiinae along the circular and radial nerves, but chiefly 

 along the lateral ventral radii. Of great interest is the relation of the 

 stone-canal to the body-wall in this family. The primitive condition in 

 which it opens by "a single pore in front of the genital aperture is found 

 in Elpidia (some species), Kolga, and other genera. In some forms, e.g. 

 Laetmogone and Ilyodaemon (Fig. III. 9), it opens by a number of pores to 

 the exterior. The external opening has been lost in Irpa, Benthodytes, 

 and others, the canal opening to the coelom, but being still connected 

 with the body-wall. There are no retractor muscles, and no Cuvierian 

 organs. Although the Elpidiidae differ from the preceding family by the 

 generally simple, unpaired structure of the longitudinal muscles (p. 224), 



