ON FOSSIL POLYZOA. 161 



Second Report of the Committee, consisting of Professor P. M. 

 Duncan, F.R.S., and Mr. Gr. K. Vine, appointed for the purpose 

 of reporting on Fossil Polyzoa. Drawn up by Mr. Vine 

 (Secretary). 



After many laborious researches, Naturalists, generally, have accepted 

 Dr. AUman's Gymnol5;mata, for one at least of the orders of the Class 

 Polyzoa. In this order the ' Polypide is destitute of an epistomc (foot) : ';u«^/t M 

 and the lophophore is circular.'^ The order is divided into three sub- fi^/tt^i, 

 orders : — 



I. GheUostomata, Busk. = Oelleporina, Ehrenberg. 

 II. Gyclostomata, „ = TuhuUporina, Milne-Ed., Hagenow, 



I r • f Johnston. 



III. Ctenostomata, „ n. i cry—rP^'-'L^t^ ^ 

 The whole were ' founded by Professor Busk on certain structural 

 peculiarities of the cell.''^ Only species belonging to two of these sub- 

 orders are found fossil, and to these alone I shall direct attention. 



I. Cheilostomata. — Polyzoa belonging to this sub-order are ' distin- 

 guished by the presence of a movhible opercular valve.' ^ This, however, 

 is not a character on which the Paiasontologist can rely for evidence ; 

 but there are others. The ova are usually matured in external ' mar- 

 supia,' or ova-cells ; there are also appendicular organs — avicularia and 

 vibricula ; and later investigations have proved the existence of peculiar 

 perforations in the cell- walls, which Eeichert called 'Rosettenplatten,' and 

 Hincks ' communication-pores.' Through these openings the ' endo- 

 sarcal ' cord of Joliet,^ in the living Polyzoa, passed from cell to cell. 

 The aperture, or mouth of the cell, though variously shaped, is always 

 sub-terminal. To prove that Polyzoa (judging from the calcareous 

 remains) of this sub-order were present in the Paleozoic seas, it is 

 necessary that some one or other of the above-named characters should 

 be present in the species introduced as Cheilostomatous. 



II. Cyclostomata. — The simplicity of structure in this sub- order 

 precludes elaborate description. There are, however, a few points of 

 special structure to which it may be as well to direct attention. The cells 

 are invariably tubular, or nearly so ; the mouths are circular, and, 

 generally speaking, of the same diameter as the cell. The cell-mouths 

 in many of the Cyclostomata are covered by calcareous opercula, in both 

 recent and fossil species, and these are considered to be — by Mr. P. D. 

 Longe * — of an analogous character with the corneous opercula of the 

 Cheilostomata. Be this as it may — all the Cyclostomatous opercula are 

 calcareous — and their use has not yet been definitely made out. 



In his classification of the British Marine Polyzoa, Mr. Hincks bases his 

 genera and species, to a large extent, upon the shape and character of the 

 cell and ceU-mouth, — the habit of species is only of secondary importance. 

 To working naturalists amongst living species his carefully worked-out 



* Hincks' Brit. Marine Polyzoa, p. cxxxvi. - Ibid. p. cxxiv. 



' ' Corneous ' ; Waters on the rise of the Opercula. Proceed, of Manchester Lit. and 

 Phil. Sac, 1878. (Italics mine.) 



* Nervous Tissue, Miiller. 



' Oolitic Polyzoa, F. D. Longe, F.G.8., Geo. Mag., January, 1881. See also HinckB' 

 Brit. Marine Polyzoa, Introduction, p. cv, and pp. 460-1. 

 1881. M 



