ALCYONIDIUM MAMILLATUM. 495 



butcd over the surface amongst the larger imperforate 

 prominences. Smitt, misled by his diagnosis, has sepa^ 

 rated his A. hirsutum from the Cycloum of Hassall ; the 

 former he identifies with the A. mamillatum of Alder*. 

 Of the identity, however, of HassalFs species with the 

 present there can be little doubt. The arrangement 

 of the ova circularly in clusters scattered over the 

 zoarium, to which he attached so much importance as to 

 make it a generic distinction, is common amongst the 

 Alcyonidia. I have described it as it occurs in A. mytili, 

 in which the character of the reproductive cells and dis- 

 position of the ova agree perfectly with HassalFs account. 

 This author states that on more than one occasion he 

 has seen specimens of his Cycloum " enveloped in a firm 

 coating of ice •/' when it was dissolved the polypides ex- 

 panded their tentacles and displayed their usual activity. 

 Such power of enduring cold we might expect in a 

 littoral species whose principal home is in northern lati- 

 tudes. I have seen the larvae of this species liberated in 

 great numbers towards the close of January, in very severe 

 weather. 



Alcyonidium mamillatum. Alder. 



Plate LXIX. figs. 7, 8. 



Alcyonidium mamillatum, Alder, North. Cat. Trans. Tyues. N. F. C. 64 

 (sep.), pi. T. figs. 3, 4: Smitt {^^ A. hirsutum, Smitt), Nora 

 Zeiubla Bryoz., (Efr. K. Vet.-Akad. F6rb. 1878, no. 2, 11. 



Alcyonidium hirsutum, 1. Zooeciis hexagonis, a. form£B incrustantes, /3(l?. 

 forma membranacea, Smitt, loc. cit. 497 & 51 1 , pi. xii. figs. 6, 6. 



Zoarium a rather thick crust, semitransparent, brownish. 

 Zooecia ovate, the anterior extremities produced into 



* Polvzoa of Nora Zembla, O^i'v. K. Vet.-Ak. Forb. 1878, no. 3, 11. 



