504 G. R. Vine—Carboniferous Polyzoa. 
Millepora rhombifera, Phill., Geol. Yorkshire. 
Fe gracilis » Paleozoic Foss. 
Both Ceriopora, Morris, Catalogue. 
Rhabdomeson gracile and R. rhombiferum, Young and Young. 
Gen. Ch.—R. gracile. “Stem slender, cylindrical, branching at 
right angles to the stem never less than an inch apart; and consists 
of a hollow axis formed by a thin calcareous tube, and of a series of 
cells ranged round the axis . . . apertures of cells, oval . . . ridges 
tuberculated.”* 
R. rhombiferum. “Stem slender, cylindrical, free; branches of 
nearly equal diameter given off at wide intervals . . . cells in quin- 
‘eunx all round the stem; surrounded by tubercnlated ridges... 
cell-area more numerous on one face than on the other . . . central 
axis slender, slightly flexuous, and without transverse septa.” ” 
For these two species, the Messrs. Young of Glasgow have 
founded a new genus—Rhabdomeson—on account of the peculiar 
central hollow axis which they possess, and on which the cells are 
arranged. This peculiarity is unique—for I know of no other 
Polyzoon having a rod or mesial axis similar to these. Some of the 
-Graptoloidea, sub-order Rhabdophora, Allman, possess a mesial axis, 
and so do the Rhabdopleura, class Polyzoa, order Phylactolemata ; 
but whether we should be justified in assuming on this account 
either Hydroid or Phylactolematous affinities for these fossils is a 
very serious question to decide. The assumption in either case 
would involve the discussion of many problems into which I cannot 
enter here. The Messrs. Young, in the two papers referred to, have 
gone into the question very fairly, and those who follow them in 
their critical remarks must remember that they are contending for 
the antiquity of a type of Polyzoa organization not—previous to 
their discoveries—known to exist in a fossil state. I have carefully 
followed the authors in all their investigations of this intricate 
question, but I am not prepared to use this fossil type as in any way 
indicative of the existence of Phylactolematous Polyzoa in Carbon- 
iferous times. At the same time it would be mere carping on my 
part to ignore its existence as indicative of peculiar structural 
characters that may help us in our future classification of the Palzo- 
zoie Polyzoa. 
Millepora interporosa, Phill., Geol. of Yorkshire. 
Ceriopora interporosa, Morris’ Catalogue of Brit. Foss. 
Vincularia Binniei, Etheridge, jun.* 
This species is a very variable one. Phillips speaks of it as 
having “ oval pores,” whilst the Millepora similis has more elongated 
pores ; on the other hand, Vineularia Binniei is spoken of as having 
“oval to hexagonal cells arranged in quincunx; or in: oblique 
ascending lines.” The magnified figure of a series of cells given by 
Mr. Etheridge as an illustration of his Species, is one of the rarer’ 
‘ Messrs. Young, Ann. Mag. Nat. Hist., May, 1874. 
* Ibid. 1875. 3 Grou. Maa., April, 1876. 
