ON FOsiSIL POLYZOA. 



145 



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Thamniscida^ as well. It is when we come to study the vai'ious pfenera 

 that would, in all probability, form a natural group, that several doubts 

 arise as to the wisdom of tliis arranpfcmeiit.' 



In his definition of Ilnnieni (' Brit. Mar. Pol.' p. 467), Mr. Hincks 

 savs that the ::infcia arc tubular, and this is well shown in the figure 

 o{ IT. lichnioiclfs, fig. i. pi. G7, ' Jirit. Mar. Pol.,' and also in H. viulacea, 

 fig. G of the same plate. Then, again, it is said that the ' oivcium {gonoa- 

 ciani) is a distinct chamber — not a mere inflation of the surface of the 

 zoarium, placed dorsally or in front.' These are elements of structure 

 that indicate distinct characters, and though I have not been able to 

 detect the gonoecium in any of the specimens found in the Crag, or in the 

 Miocene described by Reuss, the tubular zocccia are, in many respects, 

 similar to recent forms described by Mr. Busk (' Cyclostomata ') and Mr. 

 Hincks. Then, again, the characteristic cell orifice, with its waving lines 

 surrounding it- given by Mr. Busk ('Cyclostomata,' pi, xx. fig. 3) — is 

 entirely unlike any cell-orilice known to me in any of the species of the 

 genera named as found in the Palseozoic rocks. I do not, however, set 

 so much value upon the * wavy anastomosing ridges ' indicated by j\lr. 

 Hincks in his diagnosis of his genus Ilornrra ; nevertheless they are 

 peculiar, and may merit some consideration in our definition of species. 

 In the Pohjpora of the Carboniferous rocks there are wavy lines which 

 seem to he merely ornamentations of the surface, yet these, too, may be 

 analogous with the wavy ridges of the Hurncra of more recent times. 

 The Messrs Young, of Glasgow, in their joint paper On New Carboni- 

 ferous Polyzoa (' Ann. Mag. Nat. Hist.' May, 1875), describe as new a 

 species which they provisionally name 'fhamniscus ? Ranlcini, Y. & Y. 

 pi. ix. his, and in their remarks (loc. cit. p. 330) they say, 'The generic 

 position of the fossil is uncertain .... !^[eanwhilo, though strongly 

 disposed to regard the fossil as a true Horiicra or a member of a closely 

 allied genus, we think it safer to leave it in the Palaeozoic genus Thamnis. 

 <«,->•.' This species is certainly (superficially considered) more closely allied 

 to Ilm-nera than any Palcoozoic species known to me ; yet it, too, lacks the 

 peculiar cell orifices, though partaking somewhat of the tubular cell 

 structure of true ILirncra. In the Mcsozoic rocks — excepting a few 

 doubtful forms in the Upper Chalk — I know of no Jlorneiu or allies of 

 the genus. 



In his ' Crag Polyzoa' (p. 0.5), Mr. Busk says, 'Several fossil forms of 

 Hornvra have been noticed, and some of them figured ; but from the 

 want of precision in the details of the figures, and in the absence of 

 any determinate specific characters in the descriptions, it is extremely 

 difficult to arrive at any satisfactory conclusion respecting them. The 

 host figures are those contained in Miluc-Kdwards's excellent memoir on 

 the Crisiff!, &c. ; but even these are by no means sufficiently precise to 

 convey a correct idea of the specific differences or resemblances.' This 

 cannot be said of the species figured by ^Ir. Busk in his ' Crag Polyzoa,' 

 and I feel confident that I cannot do better than follow him in his 

 synopsis of fossil forms. 



In characterising one of his forms in the ' Bay of Naples Bryozoa,' 

 Mr. Waters draws attention to the very beautiful species which he names 

 Fillsparsa tuhHliisa,Bnsk. This is, in all probability, a variety of thelTonfera 

 viulacea, var. tabnlosa. Busk ; but, as Mr. Waters points oat (' Bay Nap. 



' Exception to tins association has boon taken by Mr. Ulrich in his contribution 

 to tlio Cinein. Joiirn. A'ut. Jlist. April 1884, and, acconliiig to hi.s views, rightly so. 

 188i. L 



