94 BRITISH PALEOZOIC SPONGES. 



characters of genera and species, based on skeletal fragments or even on detached 

 spicules merely, must be limited and provisional, but at the same time there is no 

 reason to doubt that these fragments and spicules really represent distinct species, 

 and may justly be regarded as such. 



Owing to the indefinite ideas formerly held as to the nature of fossil Sponges, 

 it has been my especial endeavour to examine the type specimens of all the species 

 hitherto described. The desirability of this revision of authentic specimens is 

 shown by the long list of bad and doubtful species given in the sequel. Of the 

 total number of reputed species of Palaeozoic Sponges up to 1883, I find that only 

 one-third belongs to the group, the remaining two-thirds being either too obscure 

 for determination or pertaining to other organisms. 



In the preparation of this part of the Monograph I have received much 

 valuable assistance from numerous friends and fellow- workers, to whom I return 

 my warm acknowledgments. The fossil Sponges preserved in the National 

 Museum at South Kensington, in the collections of the Geological Survey 

 at Jermyn Street, and at Edinburgh, and in the Woodwardian Museum at 

 Cambridge, and the University Museum at Oxford, have freely been placed at my 

 disposal; and to Dr. H. Woodward, F.R.S., Dr. A. Geikie, F.R.S., Prof T. 

 McKenny Hughes, M.A., and Prof. J. Prestwich, F.R.S., my thanks are especially 

 due for the opportunities of studying them. I am also under great obligations 

 to Mr. John Smith, Kilwinning, Mr. John Young, F.G.S., Hunterian Museum, 

 Glasgow, Dr. J. R. S. Hunter, Carluke, and Mr. James Bennie, Edinburgh, for the 

 unstinted loan of their private collections from the Carboniferous series of Scotland ; 

 whilst Mr. J. Wright, F.G.S., Belfast, sent me his specimens from the same series 

 in Ireland. Prof. R. J. Anderson, M.A., enabled me to examine the type collection 

 of supposed Permian Sponges described by the late Prof. King, and now in the 

 Museum of Queen's College, Galway. I have also received many specimens, 

 including type forms, from my friend Mr. H. J. Carter, F.R.S., Prof. H. Alleyne 

 Nicholson, F.L.S., Prof. C. Lapworth, F.G.S., Mr. G. H. Morton, F.G.S., Mr. J. 

 Thomson, F.G.S., Glasgow, and the late Mr. A. Champernowne, F.G.S. 



General Features of the British Paleozoic Sponges. 



Notwithstanding their unfavorable state of preservation, the presence in the 

 British area during Palaeozoic times of representatives of the various existing 

 sub-orders of siliceous Sponges can be undoubtedly proved ; and, in addition to 

 members of the Monactinellidse, Tetractinellidse, Lithistidse, and Hexactinellidse, 

 there are other forms, included in the Octactinellidse and Heteractinellidas, which 

 are not as yet known later than the Carboniferous period. 



