NOTES ON THE HYDROIDS OF PLYMOUTH. 397 



Sertui,aria abietina, Lhm. 

 Common in trawl refuse. 



Hydrallmania falcata, Linn. 



Very common in twenty fathoms. Two specimens only taken 

 inside the Sounds north of Batten Breakwater^ and pi'obably thrown 

 overboard by trawlers. 



Thuiaria articdlata, Pallas. 



Wembury Bay. Stones and shells off Mewstone. 



Family PLUMULAEIIDJS. 



Antennularia ANTENNiNA, Linn. 



This and the next species are common, growing on rocky ground 

 inside the Sound, and outside up to twenty fathoms. 



Antennularia ramosa, Lamarck. 



Hincks gives, as a diagnostic character of this species, " Hydro- 

 thecse separated by a single joint." This is not correct. It is in- 

 variably correct for the basal portion of a branchlet, but towards its 

 termination two joints are often seen between two hydrothecEe. The 

 same author erroneously sajs, " Gonothecae single ;" they are in fact 

 paired, one pair at the base of each branchlet. The gonothecae are 

 single in A. anfennina, and this difference affords a good specific 

 character. 



Aglaophenia tubulifera, Hincks. 



August to October. Not uncommon from Wembury Bay and off 

 the Mewstone. I am not quite sure of the identity of this species. 

 In most of the specimens I examined the corbula has invariably the 

 spur mentioned by Hincks as characteristic of this species, but the 

 hydrothecae are exactly those of A. pluma, everted, patulous, and 

 strongly dentated, quite unlike those of A. tubulifera, Hincks. 



Aglaophenia pluma, Linn. 



Common on the fronds of Halidrys siliquiisa, Bovisand Bay, and 

 off Mewstone. 



