96 



CCELENTERATA 



iii'ejj;ularly placed. (Jonosome: i^onoplioies usually amoni;- the basal 

 tentacles and producing either t'ree-swiuiming or attached medusae with 

 4 radial ciuials and 4 tentacles: nunierous genera. 

 Key to the genera oi' Corynidae heie described: 



fli Il.vdroid branched: medusa with 4 Ions, maruinal tentacles 1. Syncgryne 



(/, llydioid branchod ; medusa with 4, short kuohbi'd marginal tentaeles. 



2. DiPURENA 



Ca Ilydroid not branch(>d ; medusa with 2 h)Uj,' and 2 rudimentary marginal 

 tentacles ^- OeMxMARIa 



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

 and with dehnite 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 mirahilis^ 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 Avithout ocelli or mouth. 



2. DiPURENA McCrady. Hydroid like Syn- 



fi \ corijYie; 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. strangulata 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. BOUGAIlSrvn.LIIDAE. 

 Trophosome: colony branching with distinct, often annulated pen- 

 sarc; hvdranth with a single whorl of filiform tentacles. Gonosome: a 



Fig. ir)4 — Fyncorifne 



mirabili'i ; medusa 



(Hargitt). 



Fig. 155 



Dipurena stran- 



yulata 



(Hargitt). 



