HARD WICKE'S SCIENCE- G OS SI P. 



109 



by the same authors, in the "Annals of Natural His- 

 tory," vol. xiii., on a new genus of Carboniferous 

 Polyzoa, in which the authors examine the generic 

 value and affinities of the genus Ceriopora with spe- 

 cial reference to the Carboniferous JMillcpora gracilis 

 {Ceriopora gracilis of Morris). This species they con- 

 clude to be entitled to separation from Ceriopora, 

 however this genus may be ultimately defined. They 

 therefore projDose the name RhabdoDicson gracilis for 

 this form.* . 



Fig. 94. Polypora 

 tiibcrculnta. 



Fig. 95. Portion of ditto, 

 magnified. 



Fig. 96. RctcJ>oya Trenioni- 

 eusis, nat. size. 



Fig. 97. Ditto, mag 

 nified. 



As all, or nearly all, of the genera and species of 

 the Carboniferous Polyzoa are become extinct, it will 

 be necessaiy to give the generic characters in a con- 

 nected form ; reserving the specific differences for 

 another paper, with a few illustrations of the more 

 common species, together with their range in space, 

 more especially in the British carboniferous strata. 



Fenestella, Miller. — Cup-shaped, conical, 

 formed of thin carinated (keeled) radiating ribs, 

 connected by transverse, non-poriferous bars ; two 

 rows of prominent pores on the external carinated 



* See also paper on Hairmj're's Polyzoa in the " Edinburgh 

 Geological Transactions," 1874. 



face of each interstice. In his introduction to his 

 genus Retepora (Fenestella), Phillips says the open- 

 ings in the network are called " fenestrules " ; the 

 spaces between the ends of these, "dissepiments"; 

 those between tlie lines of fenestrules, "inter- 

 stices." 



There are a few more papers in the "Geological 

 Magazine " and the " Proceedings of the Geologists' 

 Association," and this is nearly all of the English 

 literature that I am aware of in which descriptions 

 and figures of Carboniferous Polyzoa are given. Lists 

 may be found in Armstrong's " Carboniferous Fossils 

 of the West of Scotland," in the "Memoirs of the 

 Geological Survey," especially in the explanation of 

 sheet 23 (Scotland), and also in Morris's " Catalogue 

 of British Fossils." 





Fig. 98. Fenestella iin- Fig. 99. Glaiicoiioiite Fig. 100. Out- 

 dulaia (magnified). plniiia. line of ditto. 



Fig. loi. Fi-ncsiella 



(Devonian Species), 



nat. size. 



Fig. I02. Ditto ^magnified) ; 

 non-poriferous side only. 



Retepora, Lamarck.- — The coenoecium, or face, 

 fan-shaped ; in place of transverse "dissepiments," 

 the branches of the coenoecium unite with one another 

 in such a manner as to form ovate interspaces of 

 "fenestrules." The outer surface of the coenoecium 

 is non-celluliferous, and minutely striated. The inner 

 surface bears several rows of small cells. 



Ptilopora. — A feather-like arrangement. A 

 central stem giving off lateral branches, \vhich are con- 

 nected by dissepiments, leaving oval fenestrules ; ex- 

 ternal face of the interstices carinate, and bearing two 

 rows of pores. Fig. in Page's " Litroductory Text- 

 book," p. 81. 



Glauconome, Goldfuss, restricted by Lonsdale. — 

 Stem elongate, oval, laterally branched, bearing 

 longitudinally-disposed cellules, but which are not 

 united by transverse dissepiments ; reverse striated. 

 In another description of the genus it is stated " that 

 both stems and branches have two rows of cells on 

 one face, which is usually carinated between them ; 

 in some species a row of small cells on the keel." 

 This genus is the Acanthocladia of King. 



Archimedipora. — Two figures of this genus are 

 given in Dana's "Manual of Geology," as common 

 in the United States. The ccenoecium is wound 

 round in an oblique column, or spiral, on a central 



