426 ECHINODERMS OF THE BRITISH ISLES 



Key to the genera of Synaptince known frotn or likely 

 to occur in the British seas. 



1. Calcareous bodies (anchors and anchor phites) present . 2 



,, ,, absent .... RhahdomoUjus Kef. 



2. Anchor plate narrowed into a distinct handle (Fig. 258) 



2. Labidoplax Ostergren 

 Anchor plate not narrowed into a distinct handle . . 3 



3. Anchor plate irregular, wath numerous small holes (Fig. 260) 



Protankyra Ostergren 



Anchor plate more regular, with larger, regularly arranged holes 



(Fig. 2G2) ..... 1. Leptosynapta Verrill 



Fig. 260. — Anchor plate of Protankyra abyssicola. x 70. 

 (After H. L. Clark, Apodous Holothurians.) 



1. Leptosynapta Verrill. 



Basal part of anchor plate gradually narrowing, not having 

 the shape of a narrow handle, sharply set off from the outer part 

 of the plate. 



Transparent forms, of small or moderate size, which live 

 buried in the ground, in sandy or muddy bottom. They feed 

 on the bottom material, which they ingest by means of their 

 tentacles. 



Only one species is known from the British seas, but four 

 other species are very likely to be found there also, namely, 

 Leptosynapta bergensis Ostergren, known from the Trondhj em- 

 fjord to Heligoland, as also from the Faroe Islands ; L. de- 

 caria (Ostergren), known from Trondhj emfjord to the Kattegat ; 



only a fragment without any. calcareous deposits. It is exceedingly im- 

 probable that this was really identical with the West Indian littoral 

 Synaptula hydrijormis, and there is no reason to expect this species to be 

 represented in European seas. 



