HOLOTHURIOIDEA 



433 



Fig. 264. — Anchor and anchor 

 plate of Labidoplax Buski. 

 X 200. (From Danmark's 

 Fauna.) 



vessel. No muscular stomach. Gonads only one long, un- 



branched tube on each side the dorsal mesentery ; genital 



opening at the base of the dorsal tentacles. Ciliated funnels 



appear to be wanting. Calcareous ring consisting of 11 pieces, 



there being 2 interradialia in the mid-dorsal interradius. Radials 



perforate. Anchors narrower than 



the anchor plates ; the latter of a 



fairly regular shape, with 6 serrate 



holes of about equal size ; the handle 



narrow, with one or two more or less 



slit-like holes (Fig. 264). Colourless, 



or, Avhen the genital organs are 



strongly developed, faintly reddish - 



yellow. Reaches scarcely more than 



ca. 3 cm. length. 



Lives in muddy bottom. De- 

 velopment unknown ; but the large, 



yolky eggs would seem to indicate that the development is direct, 

 without an Auricularia stage. In young specimens Auricularia 

 wheels may occur in the posterior end, even in specimens up to 

 2 cm. long. 



In British seas this species is known only from the Clyde and 

 the Hebrides (Sound of Harris). It is elsewhere distributed from 

 Finmark to Kattegat on the Scandinavian coasts, in depths of 

 ca. 10-420 m. 



2. Labidoplax digitata (Montagu).^ 

 (Figs. 265, 266.) 



(Syn. Synapta digitata Mont.) 



Tentacles usually 12, with 2 pairs of 

 lateral digits, the outer the largest ; the 

 terminal digit is rudimentary or absent. 

 The inside of the tentacle presents two 

 longitudinal series of small round sensory 

 organs (Fig. 265), and at the base a small 

 pigmented spot (eye ?) between the ten- 

 tacles. The alimentary canal forms a 

 loop ; muscular stomach present. Gonads 

 dichotomous tubes. Genital opening at the 

 base of the dorsal tentacles. Ciliated 

 funnels small, but very numerous, in a 

 series throughout almost the whole body length in the mid-dorsal 



1 A good figure of the animal is given in Bell's Catalogue, PI. VII. 1-2. 



Fig. 265.— Tentacle of 

 Labidoplax digitata, 

 showing the two 

 groups of sensory 

 organs, x 10. (After 

 Cuenot, Contrib. 

 Faune d'Arcachon : 

 Echinodermes. ) 



