HOLOTHURIOIDEA 



405 



and the jjlates are reduced in size. Colour whitish ; the skin 

 transparent, the internal organs being discernible through the 

 skin. Does not grow to a larger size than ca. 3 cm. length. 



The variety abyssalis Koehler, from 

 the Bay of Biscay, 650 m. (" Caudan "), 

 differs from the typical form in the 

 spire being much shorter, conical. 

 (Cf. Echinod. " Caudan'\ PL II. 22.) 



It lives on muddy bottom, probably 

 buried in the mud, with only the mouth 

 and anal prolongation above the ground 

 surface. Development unknown. 



In British seas this species is known 

 only from off the Irish w^est coast, 

 from ca. 750-1430 m. (" Porcupine ", 

 " Helga "). It is also recorded from a 

 depth of 2172 m. off S.W. Ireland 

 (" Porcupine "), but this is more prob- 

 ably Sphcerothuria talismani. The 



species is elsewhere distributed from North Cape to the Bay of 

 Biscay. The statements of its occurrence in the West Indies 

 and off South Africa are probably due to confusion with 



Fig. 242. — l.Echinocucumis 

 hispida. 2. Thyone raph- 

 aniis. Nat. size. (From 

 Danmark's Fauiia.) 



Fig. 243. — Calcareous deposits of Echinocucuniis hispida. 

 (From Danmark''s Fauna.) 



50 



Sph. talismani (or other species ?). The bathymetrical distri- 

 bution is ca. 50-ca. 1400 m. ; it cannot be said exactly to how 

 great depths it is known to descend, because there has evidently 

 been a great deal of confusion between this species and Sphcero- 

 thuria talismani ; the specimens from the greater depths may bo 

 expected to be, mostly at least, Sph. talismani. 



3. Thyone Oken. 



Body usually thick, ovoid, more or less attenuating, especially 

 towards the posterior end. Body wall thin, soft. None of the 

 lateral tentacles enlarged. Tube-feet spread all over the body, 



