114 M. K. A. Zittel on Fossil Lithistidce. 



attempted ; and it is left to the reader to summarize the obser- 

 vations made on the different species and to constmct from 

 them genera, families, &c. Quenstedt's monograph consists 

 solely of descriptions of species ; generic names are, indeed, 

 occasionally proposed for particular groups, but are rarely 

 consistently retained in the text, and never defined by dia- 

 gnoses. 



In the case of the latticed sponges the living Hexactinel- 

 lidse are occasionally referred to ; but with respect to all other 

 forms we find no indications of their position relatively to the 

 sponges of the present day. In Quenstedt's latest publica- 

 tion, therefore, the fossil and living sponges are just as uncon- 

 nected as in the works of Goldfuss, Michelin, D'Orbigny, Fro- 

 mentel, &c. Admirably as Quenstedt brings out, by nume- 

 rous figures, the external appearance and, in part, also the 

 canal-system of the Upper Jurassic Lithistidae, which are 

 chiefly comprised under the generic names Siphonia, Cnemi- 

 dium [Cnemispongia)^ Tragos^ and Planispongia^ we never- 

 theless gain not the least instruction as to their finer structural 

 characters and systematic grouping. Hence the following 

 investigations, carried out upon a different method and from 

 different points of view, cannot be rendered superfluous by 

 Quenstedt's monograph. 



For the first certain evidence of the existence of fossil 

 Lithistidse we are indebted to Oscar Schmidt *. Soon after- 

 wards (1871) H. J. Carter f recognized certain isolated sili- 

 ceous bodies from the Greensand of Haldon as remains of 

 Lithistidse. Forked anchors and quadriradiate skeletal cor- 

 puscles of Lithistidse are figured by Perceval Wright % from 

 the Chalk of Ireland, and by Rutot § from the Eocene sands 

 of Brussels. Lastly, in a memoir on the fossil sponge-genus 

 Pharetrospongia^ W. J. Sollas H states that the genera 

 Siphonia and Polypothecia belong to the Lithistidse. 



I have now occupied myself for more than two years almost 

 exclusively with the study of fossil sponges, and have already, 

 at the annual meeting of the German Geological Society at 

 Jena in the autumn of 187611, and also at the fiftieth meeting 



* ' Grundziige einer Spongienfauna des atlant. Gebietes/ 1870, p. 24. 

 t Ann. & Mag. Nat. Hist. ser. 4, vol. vii. p. 112. 

 \ Rep. Belf. Nat. Field Club, 1873-74, Append, pi. ii. figs. 16-18, 

 pi. iii. figs. 2, 3, 8-10. 



§ Ann. Soc. Malac. Belg. tome ix. pi. iii. figs. 9-11, 22-26, 43, 45, 46. 



II Quart. Journ. G-eol. Soc. vol. xxxiii. (1877) p. 252. 

 ^ Zeitschr. deutsch. geol. Gesellsch. Bd. xxviii. p. 631. 



