ON FOSSIL POLTZOA. 145 



Thamniscidfe as well. It is when we come to study the various genera 

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

 arise as to the wisdom of this arrangement. 1 



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

 says that the zooecia are tubular, and. this is well shown in the figure 

 of H. lichenoides, fig. i. pi. 67, 'Brit. Mar. Pol.,' and also in H. violacea, 

 fig. 6 of the same plate. Then, again, it is said that the ' oeecium (gonce- 

 cium) 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 zocecia 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-orifice known to me in any of the species of the 

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

 so much value upon the ' wavy anastomosing ridges ' indicated by Mr. 

 Hincks in his diagnosis of his genus Homera ; 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 be merely ornamentations of the surface, yet these, too, may be 

 analogous with the wavy ridges of the Homera 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 Thamniscus ? Banhini, Y. & Y. 

 pi. ix. his, and in their remarks (he. cit. p. 336) they say, ' The generic 

 position of the fossil is uncertain .... Meanwhile, though strongly 

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

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

 ats.' This species is certainly (superficially considered) more closely allied 

 to Eornera than any Palceozoic species known to me ; yet it, too, lacks the 

 peculiar cell orifices, though partaking somewhat of the tubular cell 

 structure of true Homera. In the Mesozoic rocks — excepting a few 

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

 the genus. 



In his ' Crag Polyzoa ' (p. 95), Mr. Busk says, ' Several fossil forms of 

 Homera 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 

 best figures are those contained in Milne-Edwards's excellent memoir on 

 the Crisiae, &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 Mr. 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 beaut iful species which he names 

 Fdisparsa tuhulosa, Busk. This is, in all probability, a variety of the Homera 

 violacea, var. tuhulosa, Busk; but, as Mr. "Waters points out (' Bay Nap. 



' Exception to this association has been taken by Mr. Ulrich in his contribution 



noo7 CWi- Jmrn - 2Vat ' ]Hst - A P ril 1884, and, according to his views, rightly so. 



1884. L 



