396 NOTES ON THE HYDROIDS OF PLYMOUTH. 



its very large, deep browiij and absolutely non-retractile polyps. 

 It grows on flat stones at a depth of seven fathoms. It is closely 

 allied to the genus Halecium, which it resembles in the form of the 

 polyp and the character of the hydrothecae ; in habit it comes 

 nearest to H. tenellum. The ringing of the stem, the pedicillate 

 hydrothecae, and the non-retractile polyp, which is relatively much 

 larger than the partially retractile polyps of the genus Halecium, 

 are sufficient to warrant its being placed in a distinct genus. I 

 have named the species after Professor E. Ray Lankester, to whose 

 energy and enthusiasm the Marine Biological Association owes its 

 existence, and to whom I am personally indebted for much kindness 

 and advice. 



Halbcidm Beanii, Johnston. 



Very common. Duke Rock. Bigbury Bay. Oif the Mewstone. 



Halecidm halecinum, Linn. 



Very common, and generally taken with the preceding species. 



Family SERTULARIID^. 



Sertulaeella polyzonias, Linn. 



Common and generally distributed on clean stony ground, seven 

 to twenty fathoms. 



Sektularella Gayi, Lamoureux. 



Wembury Bay. Cawsand Bay. Duke Rock. Eddystone. Common. 



Diphasia pinaster, Ellis and Solander. 



Very common in trawl refuse. South of Eddystone. 



Sertularia argentea, Ellis and Solander. 



Plymouth Sound. Start Point. Trawl refuse from Eddystone. 



Sertularia pumila, Linn. 



Growing in profusion on rocks and weeds between tide-marks. 



SeRTDLAEIA CUPRESSINA, Li7in. 



Common in trawl refuse from the Eddystone, and very common 

 in forty fathoms near the Wolf Rock. 



