74 The Genera of the Plumulariidoe, 



new genera, with a list of all the species previously described,, 

 and much valuable information respecting the histology of 

 those which the author has studied. I propose to make 

 some further remarks regarding these works before the con- 

 clusion of the present paper. 



II — Classification of the Plumulariid^. 



In the " Challenger" Report Professor AUman divides the 

 Plumulariidge into two principal sections or sub-families, 

 the Eleuthero'plea and the Statoplea. The first of these 

 corresponds to the genera Plumularia and Antennularia of 

 Mr. Hincks and later authors, with such recent genera as 

 are nearly allied to them ; the second consists of the Aglao- 

 phenia of Hincks and Kirchenpauer, with some other genera 

 possessing the same general type of trophosome. In the 

 Eleutheroplea the lateral sarcotheca3 are almost invariably 

 movable, and none of those which surround the hydrotheca 

 are actually attached to it; in the Statoplea, on the 

 contrary, the lateral, and generally the anterior sarcothecas, 

 are in contact with the hydrotheca for at least a part of 

 their length, and none of them are movable. The hydro- 

 thecse in the Eleutheroplea are usually more or less cup- 

 shaped, with the margin plain, or occasionally sinuated, but 

 not toothed, and are in most cases set at some distance apart, 

 so that the hydrophyton has a graceful, slender aspect ; 

 while those of the Statoplea are generally closely set on the 

 hydrocladia (or hydrotheca-bearing ramules), and are fur- 

 nished with teeth or lobes on the margin. But none of 

 these distinctions can be relied upon invariably, as several 

 Statopleans have distant hydrothecse with smooth margins, 

 while some Eleutheropleans have closely-ranked hydrothecse 

 with sinuated margins, and Professor Allman says that at 

 least one species has the margin distinctly toothed. There 

 appears to be, in fact, no single characteristic to which we 

 can point as invariable. I thought to have found such a 

 distinction in the fact that the supracalycine sarcothecee of 

 Statopleans when present are wholly or partially attached 

 to the hydrotheca, while in the Eleutheroplea they are not 

 so attached ; but Halopteris is perhaps an exception to the 

 latter rule, and in some Plumularians the supracalycine 

 sarcothecEe are entirely wanting. But notwithstanding tha 

 difficulty of framing definitions which would be universally 

 applicable, it is in most instances easy to refer a species to 



