252 CORDYLOPHORA LACUSTRIS. 



Ehrenberg erroneously referred Cavoliiii's liydroid, and lie has in this respect been followed by 

 Agassiz, who, moreover, refers to it the species of the genus Cordi/Iojj/iora, which, no less than the 

 Sertularia parasitica of Cavolini, are absolutely excluded from it. 



But in order that the genus Syncoryne may admit these forms, Agassiz finds it necessary 

 to modify it by removing from it all the si)ecies included in it by Ehrenberg except the Serfularia 

 parasitica of Cavolini, which, as has just been said, was erroneously placed there by Ehrenberg. 



Now this reconstruction of Syncoryne in a sense in which the genus was not understood by 

 its founder is inadmissible, but even supposing it allowed, I must still differ from the distin- 

 guished North American zoologist in his generic association of Cordyhphora with the Serfularia 

 parasitica. 



The Sertularia parasitica already taken by Van Beneden as the type of a new genus, 

 Corydendrium, Van Ben.,^ is certainly a very remarkable hydroid, and though much is still needed 

 for a satisfactory knowledge of it, we can gather from the figures and description left by Cavolini 

 that it has a curious complex hydrophyton, that it has a singularly extensile and dilatable pro- 

 boscis, and that its gonophores are phanerocodonic. In all these points Cavolini's hydroid stands 

 widely separated from the species of Cordylophora, so widely that it cannot be associated with 

 them in a common generic group. 



1. COBDYLOPHORA LACUSTRIS, Alhiaii. 

 Plate III. 



TuBtiLAKiA CORNEA ? — AijarHi, Kongl. Vetensk. Ak. Forhandl. Stockholm, 1816. 



Cordylophora lacustris, — Allman, Brit. Assoc. Reports, for 1843; Phil. Trans., 1853, p. 



367, pi. XXV and xxvi. Hincks, in Ann. Nat. Hist., 

 for March, 1853; and Brit. Hydr. Zooph., p. 16, pi. iii, 

 fig. 2. Van Beneden, in Bui. Ac. Roy. de Belg., 2me 

 ser., vol. xxiii. No. 5, 1867. F. E. Schulze, Ueber 

 den Bau und die Enwicklung von Cordylophora 

 lacustris, mit sechs Kupfertafeln, Leipzig, 1871. 



SvNCORVNA lacustris, — Agussi:, Coutr. Nat. Hist. U.S., vol. iv, p. 339. 



TEOPHOSOME. — HrDROCAULUS alternately branched, attaining a height of from 

 two to three inches ; perisaec gradually losing itself on the neck of the hyclranth, and 

 with shallow annulations at the origins of the ultimate ramuli. Hydranths with 

 about sixteen tentacles. 



GONOSOME. — Gonophores obovate, invested by an extension of the perisarc ; on 

 short stalks, springing from the sides of the ultimate ramuli on which they are alter- 

 nately disposed. 



Colour. — Hydranth nearly colourless, but with a pale reddish-brown tint ; gonophores with a 

 reddish-brown spadix ; perisarc brown in the older parts, pale straw colour in the younger. 



' 'Bull. Acad. Brux.,' 1844. 



