ECHINODERMATA OF NEW ENGLAND. 35 



Perigonemus. Coenosarc chitinous. Stem branching 

 with thread-like stolon. Single verticil of tentacles ; gon- 

 ophores developed from ccenosarc. 



Medusa, Stomatoca. 



Bougainvillia. Stem branched, rooted by filiform 

 stolon. Co3nosarc with chitinous covering. Single circle 

 of tentacles round base of conical proboscis. 



Medusa, Nemopsis and Bougainvillia. 



N. Bachei. 

 B. superciliaris. 



Cladonema. Stem simple, slightly branched. Four 

 capitate, tuberculate tentacles, from false tentacles which 

 are stiff, and rounded at the extremities. 



C. radiatum. 



Stauridium. Creeping stolons, stem simple. Four 

 whorls of cruciforrnly arranged tentacles, which are rigid, 

 extending at right angle to the body. 



iSyncoryne. Stem simple or branched, rooted stolon 

 wholy covered in tube. Medusa is Sarsia. 



S. mirabilis. 



C. 



Hydrichthys. Parasitic on body walls of a fish. No 

 tentacles ; no terminal mouth opening. Sexual clusters, 

 botryoidal. 



H. mirus. 



Thecaphora. 



A. 



Ophiodes. Stem, branching, base enclosed in cup ; sto- 

 lon root-like ; non-retractile hydranths which are divided 

 by a constriction into two regions. Webbed tentacles in 

 a single verticil. 



0. mirabilis. 



