HOLOTHUPvIOIDEA 409 



small ones in each radius ; the latter are placed nearer the 

 mouth, there being thus two circles of tentacles. 



Two genera of this subfamily are known from the British 

 seas ; a third, PhyllopJiorus, with the species Ph. urna Grube, is 

 a littoral form, known only from the Mediterranean. There may, 

 perhaps, be some possibility of finding this form in the adjoining 

 regions of the Atlantic, and it may, in any case, be desirable to 

 include it in the key to the genera of the Phyllophorince, the 

 more so as the genus Thyonidium has, apparently erroneously, 

 been united with PhyllopJiorus} 



Key to the genera of Phyllophorince known from or possibly 

 occurring in the British seas. 



1. Tube-feet confined to the radii . . 1. Pseudocucumis Ludw. 



,, spread all over the body ..... 2 



2. Five pairs of large tentacles in the outer circle and 5 pairs 



of small ones in the inner circle ; calcareous ring without 

 posterior prolongations . 2, Thyonidium Diib. and Kor. 



Outer circle of large tentacles with more than 10 (12-15), not in 

 pairs. Inner circle with usually only 5 single small tentacles ; 

 calcareous ring with posterior prolongations 



Phyllophorus - Grube 



1. Pseudocucumis Ludwig. 



Tentacles 20 (18), the 10 (8) smaller alternating with the 

 larger or forming an inner circle. Tube-feet confined to the 

 ambulacra, only rarely a few tube-feet may be found scattered 

 in the interradii in the middle of the body. Both radiaha 

 and interradialia of the calcareous ring may have posterior 

 prolongations. 



One species known from the British seas ; another species, 

 Ps. Marioni (v. Marenzeller) (Sjni. Cucumaria Marioni v. Marenz.) 

 is known from the Mediterranean and may possibly be expected 

 to occur also in the adjoining Atlantic region. ^ 



1 Miss Deichmann has recently undertaken a revision of Phyllophorus 

 and Thyonidiuyn, and has kindly informed the author of her results and 

 allowed him to include them in the present work. The detailed report on 

 these studies will appear in the forthcoming report on the " Ingolf " 

 Holothurians. 



2 For a description of Phyllophorus urna see Koehler, Echinodermes, 

 Faune de France, p. 169. It may be recalled here that this species is 

 viviparous. 



3 For a description of this species see Koehler, Echinodermes, Faune de 

 France, p. 169. 



