90 AMERICAN HYDBOIDS. 



Distribution. — This is a very abundant spocies in shallow water on British and European 

 coasts as well as on the Atlantic Coast of the United States from Labrador to the Carohnas. It 

 has been reported from the Mediterranean (Heller) and the coasts of France (Beltencourt, 

 according to Broch). Numerous authorities report it from northern waters, e. g., Norway, 

 (Bonnevio); Iceland (Saemunds^on) ; Shetland Islands (Norman); Arctic Sea (Bergh). 



American records are also numerous, it being reported on the Atlantic coast from Labrador 

 (Packai-d); New England (Verrill, Fewkes, etc.). The records from the Pacific coast are widely 

 scattered, e.g., Puget Sound (Calkins); CaUfornia (Jaderholm); Patagonia (Jaderholm); Central 

 American coast, Pacific (Clarke). 



This species has been very carefully studied and figured by Hartlaub (Hydromedusen 

 Helgolands, 1897) who considered its gonosome so different from that of other Campanularidse 

 that he instituted for it the genus Obelaria. He claimed that the species does not produce 

 medus£e; but this view does not seem to be corroborated by other waiters, although it is con- 

 fii-med by the specimens before me. 



It seems evident that the species figured and described as C. gelatinosa by van Beneden 

 is the same as that described as Obelia longissima by Hincks. 



Bathymetric distribution, 1 to 30 fathoms. 



Genus SILICULARIA Mayen (part). 



Silicularia Mayen, Uber das Leuchten des Meeres, 1834, p. 204. 

 Hypanihea Allman, Challenger Reports, Hydroida, pt. 2, 1888, p. 25. 



TropJiosome. — Hydrothecal walls greatly thickened, leaving a cavity too small to admit 

 of complete retraction of the hydranth. Hydrothecse often bilaterally symmetrical owing to 

 an oblique margin. 



Gonosome. — Gonangia (male) very long and slender. Female gonangia contain fixed 

 sporosacs which produce planulte. 



The above definition is practically that of Alknan as given for his genus Hypanthea, founded 

 on Challenger specimens. The generic name Silicularia was applied, however, in 1834 to a 

 species clearly coming within the genus defined as HypantJiea by Allman. 



Hartlaub, in his "Die Hydroiden der magalhaensischen Region und chilenischen Kiiste" 

 (1905, pp. 371, 372), gives a very interesting discussion of this genus, throwing some doubt 

 on its validity as defined by Allman, but nevertheless accepting it in his work. The present 

 writer has not sufficient material of tliis genus to undertake an independent investigation and 

 contents himseK with the above definition. 



This genus is found only in the Southern Hemisphere, and most of the species are in the 

 subantarctic region. 



KEY TO THE AMERICAN SPECIES OF SILICULARIA. 



Hydrothecse regularly campanulate pedunculata. 



Hydrothecse ■with oblique margins. 



Creeping stolons parallel, contiguous rosea. 



Stolons not closely contiguous and parallel, forming an open irregular mesh reticulata. 



Lumen of hydrothecse nearly hemispherical hemispherica . 



Lumen of hydrothecse not hemispherical. 



Male gonangia longer than the female repens. 



Male gonangia shorter than the female , atlantica. 



SILIcaLARIA PEDUNCULATA (Jaderholm). 



Plate 24, figs. 6-8. 



Campanularia pedunculata Jaderholm, Archives de Zoologie exp^rimentale et g^n^rale, 4e serie, vol. 3, 1904, p. vi. 

 Silicularia divergem Hartlaub, Die Hydi'oiden der magalhaensischen Region und chilenischen Kuste, 1905, p. 578. 

 Silicularia pedunculata Jaderholm, Hydroiden aus antark(ischen and subantarktischen Meeren, 1905, p. 18. 



TropTiosome.^ — The rootstock is not present in the specimen described, but accordmg to 

 Hartlaub the stolon is broader and. thinner-walled than the pedicel walls. Pedicels long, slender, 



' Description of a specimen mounted on a slide and kindly loaned me by the describer of the species, Dr. C. Hartlaub. 



