[175] THE HYDROIDS Ip3 



HEBELLA. 



Trophosome. Pedicels arising from a creeping rootstock, very 

 short. Hydrothecae tubular, with entire margins, without opercula, 

 and having their cavities separated from those of the stems by a partial 

 septum. Hydranths with a conical proboscis. 



This genus was originally instituted by Allman. 1 As here defined 

 it includes several species heretofore included in the genus Lafcea. 



HEBELLA POCILLUM (Hincks). 



Lafcea porillum HINCKS, British Hydroid Zoophytes, p. 204, 1868. CLARK, 

 Proc. Acad. Nat. Sciences, Philadelphia, p. 215, 1876. VERRILL, Pre- 

 liminary check-list Marine Vertebrates of Atlantic coast, p. 17, 1879. 

 BERGH, Goplepolyper (Hydroider) fra Kara-Havet, p. 333, 1887. 



Distribution. Kadiak. Alaska (Harriman Exped.) ; Nunivak 

 Island, Alaska (Clark) ; Kara Sea (Bergh) ; British Coasts (Hincks) ; 

 New England Coast (Verrill). 



GONOTHYILEA. 



Trophosome. Much as in Obelia. 



Gonosome. Planulae produced in sessile medusaform gonophores 

 which remain attached to the top of the gonangia until the spermatozoa 



or planulae are discharged. 



GONOTHYIL/EA INORNATA sp. nov. 

 (Plate xx, figs. 2-4.) 



Trophosome. Colony attaining a height of about two inches and 

 consisting of a main stem which almost immediately breaks up into a 

 number of very slender, erect, almost straight branches which are 

 ornamented with about three annulations immediately above the origins 

 of the pedicels. Pedicels alternate, erect, much broader below than 

 above and with seven to ten annulations. Hydrothecae funnel-shaped, 

 with entire margins. 



Gonosome. Gonangia borne in the axils of the pedicels, slender, 

 obconic, with a tendency to annulation. Each gonangium contains a 

 single sporosac which when mature rests upon the summit of the go- 

 nangium and has little indication of radial canals or tentacles. 



Distribution. Yakutat Bay, Alaska (Harriman Exped.). 



This species differs from others of the genus in having but one 

 sporosac to each gonangium and in the obliteration of most of the 

 medusoid characters of the sporosac. The entire margin of the hydro- 

 theca is also an exceptional character. 



1 Allman, Challenger Report, Hjdroida, Second Part, p. 29, 1888. 



