TRICHYDRID^E. 215 



lariiclse, and especially of Sertularia abietina. The calycles 

 very generally overspread the stem of this zoophyte, and 

 are often so densely and confusedly massed together that 

 it is difficult to distinguish their shape ; in such specimens 

 they form a crust, bristling with the free tubular orifices. 

 On a broader surface, where there is space for more regu- 

 lar development, the species assumes a very different and 

 a much simpler appearance ; the hydrothecse are sparingly 

 distributed, and their character is recognized at once. 

 Specimens of this kind are found occasionally on shells. 

 The calycles sometimes occur in pairs, one on each side of 

 the stem, sometimes singly, and sometimes in companies. 



Hab. On Sertularia abietina, Hydrallmania falcata, and 

 other zoophytes, and on shells occasionally; very common. 



[Off Reikiavik, Iceland, in 100 fathoms (T. H.).] 



Family V. Trichydridze. 



HYDROTHEC.E merely rudimentary, tubular ; POLYPITES cy- 

 lindrical, very extensile, with a small conical 'proboscis. 



Genus TRICHYDRA, T. S. Wright. 



Der. From 9pi (rpi%6s), hair, and Hydra, a polypite. 



GENERIC CHARACTER. Stem creeping, branched ; hydro- 

 thecae rudimentary, consisting of very short tubular pro- 

 cesses, given off at intervals from the creeping stem ; poly- 

 pites cylindrical, very slender and extensile, with a short 

 conical proboscis. 



Reproduction unknown. 



I FEEL very doubtful as to the true position of this ob- 

 scure genus. Wright would place it amongst the Corynida> 

 of Johnston, on account of the progressive development of 



