96 



CCELENTERATA 



irregularly placed. Gonosome: gonophores usually among the basal 

 tentacles and producing either free-swimming or attached medusae with 

 4 radial canals and 4 tentacles: numerous genera. 

 Key to the genera of Corynidae here described: 



! Hydroid branched; medusa with 4 long, marginal tentacles. . . .1. SYNCOBYNE 

 a a Hydroid branched ; medusa with 4 short knobbed marginal tentacles. 



2. DIPUBENA 



3 Hydroid not branched; medusa with 2 long and 2 rudimentary marginal 

 tentacles 3. GEMMABIA 



1. SYNCORYNE Ehrenberg. Hydroid colony 15 mm. high and branched 

 and with definite perisarc and an elongate, cylindrical hydranth; medusa 

 with an ocellus at the base of each tentacle : 16 species. 



S. mirabilis Agassiz (Fig. 153). Hydroid col- 

 ony attached to seaweed, shells, etc., in shallow 

 water, from Martha's Vineyard to Greenland, also 

 in California; medusoid in 2 varieties, one, which 

 was first described as Sarsia mirabilis , free-swim- 

 ming, developing in early spring, 7 mm. high and 

 4 mm. in diameter, with 4 long, marginal tentacles 

 and a long manubrium extending beyond the velum 

 (Fig. 154) ; the other, a sporosac, with rudimentary 

 tentacles, and without ocelli or mouth. 



2. DIPURENA McCrady. Hydroid like Syn- 

 coryne; medusae with 4 stout marginal tentacles 

 the ends of which are knobbed, and a long 

 manubrium with constrictions, often extending 

 beyond the velum: 6 species. 

 D. strangnlata McCr. (Fig. 155). Medusa very transparent, 3 mm. 

 wide, 4 mm. high, ovoid in shape: common at Woods 

 Hole; South Carolina. 



3. GEMMARIA McCrady. Hydroid like Syncoryne 

 but unbranched, the hydranth rising from a creeping 

 hydrorhiza; medusa with 2 marginal tentacles, each of 

 which bears long-stalked nematocysts, and with mouth 

 without marginal lobes: several species. 



G. gemmosa McCr. Hydroid on Mytilus shells, 

 etc.; adult medusa 6 mm. in diameter, almost spherical 

 and with 2 tentacles; no ocelli: Vineyard Sound and 

 southwards. 



FAMILY 3. BOTJGAINVILLIIDAE. 



Fig. 154 Syncoryne 



mirabilis; medusa 



(Hargitt). 



Fig. 155 



Dipurena stran- 

 gulata 

 (Hargitt). 



Trophosome: colony branching with distinct, often annulated peri- 

 sarc; hydranth with a single whorl of filiform tentacles, Gonosome: a 



