COPPINIA ARCTA. 63 



horny crnst The receptacles are curved, 

 bearing some resemblance in shape to the 

 old-fashioned powder horn. The lower half 

 of the receptacle is adherent to the crust. 

 F. serpens is very common on the stems of 

 other hydroids, rarely on shells. 



Family COPPINIID^E. 

 Coppinia arcta, Daiyeii. (Fio, 12.) 



1 dry specimen in box. 



SPECIMEN The receptacles are long, tubular, 



32. and curved, and are set in a horny 

 cellular crust which invests the tubes of other 

 hydroids. A comparison of sections of this 

 crust with that of Hydr actinia, and the stem 

 of Antennularia ramosa, and others, will be 

 found instructive. 



Common in the coralline zone. 



Family HALECIID^E. 



Halecium halecinum, Linnaeus. 



1 specimen dry, of exceptionally fine growth. 



SPECIMEN This has been called the herring- 



33. bone hydroid, because the stem 

 and main branches, which are compound, 

 throw out regular, alternate, lateral branches. 



