48 ECHINODERMATA. 



smaller end surrounded by tentacles ; it has four branchiae. It 

 forms the order Tetrapneumona of Schmarda [=Diplostoinidea, 

 Semper ; Decacrenidia, Bronn]. 



Some HolothuricB harbour inquilines or commensals (fish, mol- 

 lusks, crustaceans). Holothuria argus, a large black species, is 

 the trepang, or bfohe de mer, an article of considerable importance 

 as food in the Eastern seas. 



Psolidte. Thyonidium. 



Molpadia! Psolus. Phyllophorus. 



laosoma. Cu G umaria= Hemicrepis. 



Pentacta. 



Holothuriida. Thy one. ,,, . ,. ., 



Holothuria (Sea-cu- Ocnus. Khopalodimda. 



cumber). Ehopalodina. 

 Sporadipus. 



