434 M. C. Mereschkowsky on ne^o Hydroida 



SeLAGINOPSIS ( = POLYSERI as) . 



Since my article on this genus in the '■ Annals,' and a 

 short note on the same subject published a little later*, I have 

 had the opportunity of seeing the interesting article by Mr. 

 Allmanf on new Hydroids from various countries, in which, 

 among other things, that gentleman describes two new genera, 

 Selaginopsis and Pericladium. As may be seen from the 

 diagnoses and descriptions that he gives of the species of 

 these two genera, the second differs from the first only " in 

 the disposition of its hydrothecse in longitudinal series, as 

 ■well as in its totally different type of ramification " \. The 

 Rev. A. M. Norman §, who has added some species to the 

 genus Selaginopsis J accepts it in the same sense as Mr. All- 

 man has done, and separates it from the genus Pericladium. 

 Now it is certain from the species that I have been able to 

 examine, some of which have been described by me, whilst 

 others will be described in the present paper, that neither 

 from the arrangement of the hydrothecse, nor from the mode 

 of ramification, is it possible to separate the two genera from 

 each other, but, on the contrary, we find ourselves compelled 

 to unite them in a single one, in the sense in which the genus 

 Polyserias was established by me. As regards the different 

 form of ramification I may remark at once that Pericladium 

 hidentalumy for example, differs essentially fi"om Selaginopsis 

 mirabilis, one having ramifications in all planes, as in 

 Thujaria thuja, and t]ie other having them only in one 

 plane ; but as to the form and arrangement of the hydrothecse 

 they resemble one another to such a degree that it would be 

 purely artificial to separate them into two different genera. 

 As regards the arrangement of the hydrothecse " in longitu- 

 dinal series," this character is common to both genera ,• and, 

 in fact, the diagnosis of the genus Selaginopsis might be 

 accepted without the least alteration for Pericladium, and vice 

 versd. 



It is therefore evidently useless to conthiue to distinguish 

 these two genera, which I propose to unite into a single one, 

 to which I propose to give the name of Selaginopsis, as the 

 first de?cril)ed by Isir. Allman, and the one which has been 

 most employed. I will therefore pass to the description of 

 the species which I have examined. 



* Anu. & Mag, Nat. Hist. ser. v. vol. i. April and May, 1878, 



t Journ. Linn. Soc. vol. xii. (1876), p. 251. 



X Ibid. p. 272. 



§ Ann, & Mag. Nat. Hist. ser. o, vol. i, March 1878, 



