284 PROVISIONAL SPECIES. 



tentacles with lar^e, spirally arranged, closely set clusters of very elongated thread- 

 cells, the clusters increasing in size towards the extremity, where the tentacle terminates 

 in a club-shaped cluster larger tlian the others ; basal bulbs large, ovoid, each with an 

 ocellus. 



Colour of Medusa. — A very light metallic blue tinge; basal bulbs of tentacles light brown. 

 Habitat. — Growing on Biphasia rosacea. 

 Locality. — Massachusetts Bay, Alex. Agassiz. 



For the hydroid just described Mr. Alex. Agassiz has instituted a new genus, under the 

 name of Si/ndiciyon. I can find, however, nothing in his description of the hydroid to justify its 

 separation from Syiicoryne. The pecuHar network of superficial cells in the umbrella walls, which 

 seems to have suggested both generic and specific names, is an interesting histological feature,- 

 but not in itself a character which can be employed in generic diagnosis. 



Certain Sarsia-\'\\& medusae found by A. Agassiz swimming freely in the open sea are 

 regarded by him as the adult form of the medusa of the present species. They may be so, l)ut 

 the evidence is not sufficient to justify us in regarding the identity as proved. 



PROVISIONAL AND DOUBTFUL SPECIES. 

 " SvNCORYNE LiSTERii," Fan Beneden. 



The following is Van Beneden's diagnosis of this species : — 



" Tige cornea, annelee assez regulierement dans presque toute sa longueur, ramifiee. Ten- 

 tacules au nombre de seize environ." ' Recherches sur rEmlnyogenie des Tubulaires,' p. 54, 

 pL III, figs. 11, 12. 



He subsequently informs us that the medusae " sont de forme spherique et apparaissent a la 

 hauteur du verticille inferieur ;" and he adds, " ils portent pensons-nous, quatres cirrhes." 'Faune 

 Lit. de Belg.,' p. 120, pi. V. fig. 5. 



It is impossible to determine with precision the hydroid which Van Beneden had in view 

 under the designation of Syncoryne Listerii, or, indeed, to construct from the characters wdiich he 

 assigns to it, a satisfactory diagnosis ; and the difficulty is in no way diminished by tlie appended 

 .synonymes which certainly apply to a very different hydroid from that described and figured as 

 Syncoryne Listerii in either of the memoirs cited above. 



M. Van Beneden believes his Syncoryne Listerii to be identical with tlie hydroid which under 

 the generic name of Coryne, but without a specific designation, has been described by Lister in 

 the Philosophical Transactions for 1834. This is undoubtedly a wrong determination. The 

 gonophore which M. Van Beneden assigns to his Syncoryne Listerii is phanerocodonic and 

 apparently that of a true Syncoryne, though his figure shows it in too imperfectly developed a 

 stage for accurate determination ; while Lister's hydroid possesses simple sporosacs and is a true 

 Cori/ne, almost certainly the Coryne vayinata of Hincks, and of the present monograjdi. 



