ON THE CAKBONIFEROUS POLYZOA. 79 



equal diameter given off at wide intervals ... cells in quincunx all 

 round the stem ; surrounded by tuberculated 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 — Rhahdomeson — on account of the peculiar central hollow axis 

 which they possess, and on which the ceUs are arranged. This peculiarity 

 is unique — for I know of no other Polyzoa having a rod or mesial axis 

 similar to these. Some of the Graptoloidea, sub-order, Bhahdophora, 

 Allman, possess a mesial axis, and so do the Bhabdopleura — 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 organisation 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 Phylacto- 

 lematous Polyzoa in Carboniferous 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 

 Palaeozoic Polyzoa. 



Millepora interporosa, Phill. Geol. of Yorksh. 

 Ceriopora interporosa, Morris' Catalogue of Brit. Fos. 

 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 Vincularia Binniei is spoken of as having ' oval to hexa- 

 gonal cells arranged in quincunx ; or in oblique ascending lines.' The 

 magnified figure of a sei-ies of cells given by Mr. Etheridge as an illustration 

 of his species, is one of the rarer varieties of M. interporosa. Had Mr. 

 Etheridge contended for the variety, I should not have disputed his claim, 

 but as he introduces a most anomalous genus into the classification of our 

 Carboniferous Polyzoa, I cannot do otherwise than point out the anomaly. 

 Defranc's genus Vincularia had no existence whatever in Palteozoic 

 times. D'Eichwald, on whose authority Mr. Etheridge /rests, is most un- 

 reliable on this point.^ h 



It is on account of their importance that I have dwelt so fully upon 

 these species. They had a wide geographical range in Carboniferous 

 times, and though their variability is great, they have many structural 

 characters in common with the Ceriopera which range into the Mesozoic 

 and Tertiary strata. 



Under the auspices of Sir Richard Griffiths, of the Irish Geological 

 Survey, Frederick M'Coy published his ' Synopsis.' * There is ample evi- 

 dence in this work that M'Coy had much better material than Phillips, and 



' Messrs. Young, Ann. Mag. of Nat. Hist., 1875. 



' Geoloijical Mug., April, 1876. 



' See paper on Vincularidrp, mihi. Read before the Geo. Soc, June 23, 1880. 



* Synopsis of the Carh. Fos. of Ireland, 1844. 



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