[l7S] THE HYDROIDS I93 



HEBELLA. 



Trophosome. — Pedicels arising from a creeping rootstock, very 

 short. Hydrotheca; 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 original!}- instituted by Allman.' As here defined 

 it includes several species heretofore included in the genus Laftca. 



HEBELLA POCTLLUM (Hincks). 



Lafaia pocillum 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 (Ilarriman Exped.) ; Nunivak 

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

 New England Coast (Verrill). 



GONOTHYRiEA. 



Trophosome. — Much as in Obelia. 



Gonosome. — Planuke produced in sessile medusaform gonophorcs 

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

 or planulae are discharged. 



GONOTHYR^A INORNATA sp. nov. 

 (Plate XX, figs. 2-4.) 



Trophosome. — Colony attaining a height of about two inches and 

 consisting of a main stem wliich 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 annidations. Hydrothecs 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. 



' Allman, Challenger Report, Hydroida, Second Part. p. 29, 1S88. 



