Limitation of Genera among the Hydroida. 357 



rocodonic, never become free, and the marginal tentacles then 

 remain in an imperfectly developed state. 



Syncoryne Sarsii, Loven, = Syncoryne decipiens, Dujardin. 



Syncoryne ramosa, Loven. 



Syncoryne (sp.), Desor. 



Syncoryne turricula,M'Q>tQ.diy (sp.), = Sarsia turricuIa,M.'CrsLdy. 



M'Crady figures and describes the Medusa of this species ; but 

 his description of the trophosome is not full enough for a satisfactory 

 diagnosis. 



Syncoryne mirabilis, Agass. {sip. ),= Cory ne mirabilis, Agass. 



Syncoryne eximia, Allm. (sp.), = Coryne eccimiaj Allm. in Ann. 

 Nat. Hist. 1859. 



Syncoryne gravata, Wright (sp.), = Coryne gravata, Wright. 

 Provisional and Doubtful Species. 



Syncoryne hi-yoides, Ehr., = Tuhularia muscoides, Linn. 



Syncoryne Listeri, Van Ben. 



3. Zanclea, Gegenbaur. 



Trophosome. — Coenosarc consisting of a simple or branching 

 hydrocaulus rooted by a filiform anastomosing hydrorhiza, the 

 whole invested by a periderm. Polypites claviform, developed 

 from the summits of the hydrocaulus ; tentacles capitate, scat- 

 tered over the body of the polypite. 



Gonosome. — Gonophores phanerocodonic, developed from the 

 body of the polypite. Medusa, at the time of its liberation from 

 the trophosome, nearly spherical ; manubrium simple-mouthed, 

 not reaching the margin of the umbrella; radiating canals four; 

 marginal tentacles two, developed from the distal extremities of 

 two opposite radiating canals ; two intermediate bulbous dilata- 

 tions at the intersections of the two other radiating canals with 

 the circular canal ; the tentacles commence with a large bulbous 

 dilatation destitute of distinct ocellus, and are for the remainder 

 of their extent closely set along their external sides with pedun- 

 culated sacs filled with thread-cells; from the bases of the ten- 

 tacula and intermediate bulbs a csecal claviform tube filled with 

 thread-cells extends in the walls of the umbrella near its external 

 sui-face and parallel to the corresponding radiating canal. 



It is almost certain that the Medusa here described is destined to 

 nndergo considerable change before reaching its adult state, when its 

 characters will, in all probability, be those assigned by Gegenbaur to 

 his genus Zanclea. A Medusa captured by M'Crady in the open 

 sea, and regarded by him (Gymnophthalmata of Charleston Har- 

 bour) as a young state of a species of Zanclea, is almost identical 

 with that just described. 



Zanclea implexa, Alder (sp.), = Coryne implexa, Alder, = Coryne 

 Briareus, AUman, in Ann. Nat. Hist. 1859, 



