408 Annals of the South African Museum. 



then the ALERT Report's list does not throw much light on the 

 Holothurians of South Africa ! Owing to our lack of knowledge as 

 in their essential characters, I cannot include either Holotlturia maxima 

 or H. pulla in the present report. 



The 32 species of South African holothurians represent only 3 families. 

 These are easily distinguished from each other hy the following 

 characters. 



Key to the South African Families of Holothurians. 



Tentacles dendritic; retractor muscles well developed . . Cucumariidae. 

 Tentacles more or less peltate; no retractor muscles. 



No tentacle-ampullae ; no respiratory trees . Elpidiidae. 



Tentacle-ampullae and respiratory trees present. . Holothuriidae. 



CUCUMARIIDAE. 



This large and widespread family is represented in South African 

 waters by 17 species of which 13 are in the collection before me. 

 Three of the species belong in the continental fauna and one is 

 abyssal. Two seern to be new to science. Generic differences in the 

 family are not easily maintained for the genera have been largely 

 based upon the number and arrangement of the tentacles, characters 

 which show more or less considerable changes during growth. 

 The South African species fit into their respective genera well how- 

 ever, except that several of the species of Cucumaria approach so 

 close to Petitacta that the line of difference between the two genera 

 is hard to maintain. It is worthy of special note that with a single 

 exception, all the Cucumariidae of this report occur on (or off) the 

 coast of Cape Colony, or the adjoining coast of Southwest Africa 

 and of Natal. The family is thus the characteristic one for the 

 South African region. Two of the species here reported are new to 

 science, and nine others are endemic, a very unusual proportion. 

 The 17 species may be distinguished from each other as follows. 



Key to the. South African Species of Cucumariidae. 



Body wall soft or leathery, more or less filled with microscopic calcareous particles. 

 Tentacles 10. 



Ventral side of body not markedly distinct from dorsal nor are dorsal 

 ambulacral appendages larger than those of ventral side. 



Pedicels either confined to radii, or if present on the interradial 

 areas they are much smaller there. 



Inner layer of skin with numerous, often densely crowded, thick, 

 knobbed perforated plates or buttons. 



