HOLOTHURIOIDEA 423 



Dan. and Kor. ; Ankyroderma Jeffrey si Dan. and Kor. ; A. 

 affine Dan. and Kor.^ ; Molpadia Jeffreysi, var. gracilis Herouard), 

 from Spitzbergen and the Kara Sea to 62° N. in the Norwegian 

 sea, from Greenland to the West Indies ; also recorded from the 

 N. Pacific, ca. 100-1000 m. 



The great variability of the calcareous deposits in Molj^adia 

 makes the identification difficult, and has caused the establish- 

 ment of altogether too many " species ", as appears from the 

 lists of sjaionyms given above. 



Key to the species oj Molpadia Jcnown fro7n the N.E. Atlantic. 



1. Deposits smooth ........ 2 



Deposits thorny (Fig. 257, 2) {" Challenger " Holoth., ii., p. 44, 



PI. III. 2) M. albicans (Theel) 



2. Fusiform bodies (Fig. 257, 6) present all over the body (Ludwig, 



" Ankyroderma musculus ", Zeitschr. wiss. Zool. 51, 1891) 



M. musculus Risso 

 Fusiform bodies mainly in the tail, or absent ... 3 



3. Deposits larger, irregular, fenestrated plates (Fig. 257, 4-5) . 4 

 Deposits tables, usually with 3 holes and a spire (Fig. 257, 3) 5 



4. Fenestrated plates of two kinds, larger, with fewer, larger holes, 



and smaller, with numerous smaller holes (" Talisman''' Holoth., 



p. 533, PL XXII. 9-15) . . . M. maroccana (Perr.) 



Fenestrated plates of only one kind (" Talisman " Holoth., 



p. 535, PI. XXII. 23-28) "^ . . . M. loricata (Perr.) 



5. Phosphatic bodies present {Norwegian North Sea Exp. Holoth., 



p. 42, Pis. VII.-IX.) .... M. oolitica (Poiu-t.) 

 Phosphatic bodies absent ...... 6 



6. Tables very small, regular, ca. 0-10 mm. in diameter ; holes not 



pointed ; spire ca. 0T5 mm. high or more (Theel, " Blake " 

 Holoth., p. 16 ; " Monaco ", Ixvi., p. 137, Tr. grossularia) 



M. blakei (Theel) 



Tables larger, spire proportionally lower ; disks more or less 



irregular, often with prolongations, holes usually somewhat 



outwards pointed (Marenzeller, " Coelent. Echinod. Wiirmer", 



Osterreich. Nordpol-Exped., p. 29, Taf. IV.) 



M. arctica (Marenz.) 



V. Order. Apoda Brandt. 

 (Syn. Paradinopoda Ludwig.) 



Tube-feet entirely absent, even the radial water-vessels usually 

 undeveloped. Tentacles feather-shaped or with only few side 

 branches, more rarely simply digitate. Retractor muscles usually 

 absent. No tentacle ampullae ; no respiratory trees. 



1 H. L. Clark regards Arikyrodertyia affine as a separate species, 

 Molpadia affinis. 



