31K) ]^:CHIN0DERM8 OF THE BRITISH ISLES 



Ki-y to llw genera of Cucumariin<je known from or likely 

 to occur in the British seas. 



1. Tube-feet in more or less distinct series along the radii, not 



scattered all over the body ...... 2 



Tube-feet all over the body, not in distinct series 



3. Thyone Oken 



2. Body covered with large, spinous scales ; mouth and anus 



dorsal ; a pair of lateral tentacles much larger than the 

 others ......... 3 



Body not covered with large, spinous scales ; mouth and anus 

 terminal ; none of the lateral tentacles specially enlarged 



1. Cucumaria Blv^ 



3. Scales tliin, single-layered, with spine eccentric. Tube-feet not 



perforating the scales . . . 2. Echinocucumis Sars 



Scales thick, consisting of several layers ; spine nearly central. 



Tube -feet perforating the scales . . Sphcerothuria Ludw. 



1. Cucumaria Blainville. 

 (Syn. Ocnus Forbes ; Psolinus Forbes ; Semperia Lampert.) 



Body cylindrical or with 5 longitudinal ridges, often curved 

 dorsalwards, but then not strongl}^ swoUen in the middle. The 

 skin usually thick, often quite stiff on account of the calcareous 

 dejDosits ; never spinous. The two ventral tentacles usually 

 smaller than the others ; none of the lateral tentacles larger than 

 the others. Tube-feet in distinct, usually double series along the 

 radii, more rarely also on the interradii. 



The numerous species belonging to this genus wdll very 

 probably be subdivided into various smaller genera or subgenera ; 

 but till now no acceptable subdivision has been made. 



Seven species^ are known from the British seas, but three 

 more are likely to occur there also, namely, Cucumaria arcuata 

 (Herouard) (Syn. Psolidium arcuatum Her.), 32° N., 17° W., 

 1700-1968 m. (" Princesse Alice ") ; Cucumaria compressa Perrier, 

 found in the Bay of Biscay, 627 m. ("Talisman") ; and C. abys- 

 sorum Theel,2 found off the Azores (" Hirondelle "), and 45° 26' N., 



^ Cucumaria dissimilis (Fleming) Forbes and Cue. Neillii (Fleming) 

 Forbes are entirely unidentifiable, and must be left out of consideration. 

 Doubtless they are identical with some or other of the known Cucumariids 

 from the British seas. 



2 Miss Deichmann has informed the autlior that in her opinion the 

 Atlantic specimens referred to Cucumaria abi/ssorum are not reall\' identical 

 with the typical ahyssorum from the S. Pacific ; the species, which was 

 also taken by the " Ingolf ", will be described in Miss Deichmann's forth- 

 coming report on the " Ingolf " Holothurians under the name of Cucumaria 

 Ingolfi Deichm. 



