86 EEPOET— 1880. 



must be cleared up by a more complete study of all the species of the 

 Palfeozoic and Mesozoic ages of our earth's history. It is a difficult 

 matter with present classifications to place the Genera of Palfeozoic 

 Polyzoa without doing violence to constructed definitions. In the ab- 

 sence, therefore, of any well-defined families in which the Carboniferous 

 Polyzoa can be placed, I venture to group the whole of the forms under 

 separate headings, which must be considered as provisional only. But to 

 prevent any misconception as to the special characters of each group, I 

 shall refer to the shape of the cell or zooecia especially, as the basis of 

 my arrangement, allowing all the other characters to fall into their places 

 as subordinate only. 



Fam. I. — Fenestellid.4!. 



Primary Char. — Polyzoary forming small or large fenestrated or non- 

 fenestrated expansions. Cells placed biserially, or alternate, so as to form 

 branches or 'interstices,' similar in many respects to the Genus Scrv^o- 

 cellaria among living Polyzoa : cells bladder-like, margin of mouth raised 

 and covered (?) by ' operculum ' during the life of the animal. The nearest 

 living representative cell among the British Polyzoa figured by Hincks ^ 

 is that of Alcyonidium albidum, with which I can compare generally the 

 cells of the Fenestellidce. The foUovsdng genera are grouped provisionally, 

 many details having yet to be worked out : — 



Genus I. Fenestella. — plebeia, polyporafa, memhranacea, in which 

 the cells are biserially placed. 

 „ II Fenestellina — nodulosa, actinosfoma, in which the cells are 



alternate, literally forming single rows. 

 „ III. Glaucoxome — Only some of the species studied. 



Fara. II. — PoLYPORIDiE. 



Primary Char. — Polyzoary forming small and large fenestrated ex- 

 pansions. Branches robust, cells placed contiguously in a slanting direc- 

 tion over the branch, opening on one side only ; the cells on the margins of 

 the branches (younger cells) nearly of the same shape as in the Fenes- 

 tellidce ; the older cells in the innermost jiortion of the branches much 

 compressed, but never pai'taking of a tubular character. 



Genus IV. Polypora. 



The cell-structure of the following genera is such as to warrant their 

 separation from the whole of the above genera, but they are not suffi- 

 ciently studied, neither are their details so well worked out as to enable 

 me to suggest a projDer place for them at present. 

 Genus I. Goniocladia, Etheridge, Jun. 



„ II. SynocJadia, „ „ "1 Two most distinct 



Synocladia, Toung and Young. J species. 



„ III. Hyphasmapora, Etheindge, Jun. 

 ,, rV. Thamniscus, Toung and Young. 

 „ V. Sulcoretepora Bobertsoni, Young and Young. 



„ VI. ArchcBopora, De Koninck. 

 All the above are types of distinct genera, and before they can be 

 properly placed the Silurian, as well as the Permian Polyzoa must be 

 carefully studied in the way that I have already suggested. 



For the present, too, I will catalogue the remainder of the Carboni- 

 ferous Genera, reserving for the future more detailed arrangements. 

 ^ JB^'it. Marine Polyzoa, 1880, p. 500; vol. i. p. Ixx. ; vol. ii. figs. 8 to 10. 



