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



The climax of their development is attained by the Lithis- 

 tidas in the Upper Cretaceous. In Touraine and Normandy, 

 in Yorksliire, and in some districts of North Germany (on the 

 Sutmerberg, near Ahlten, Linden, Boimtsdorf, Ilsenburg, 

 Dohrnten, and Salzgitten) the multiplicity of forms of Lithis- 

 tidffi is absolutely astonishing. The genera CJionella, Selis- 

 cotJion^ Chenendopora^ Verrucidina^ Amphithelion^ BoUdium, 

 Astroholia, Stichophyma, Jereica, Coelocorypha, Scytalia^ 

 Pachiniony Doryderma^ Isorliapliinia^ Phymatella, Callopegmay 

 Traxihysycon^ Jerea^ PoJyjerea^ Astrocladia, Turonia, Rhaga- 

 dinia^ Plinthosella, Sponyodiscus^ &c. have here either their 

 exclusive or their principal liabitat. It is remarkable that the 

 Cretaceous formation has not a single genus in common witli 

 the Jura. 



On quitting the Cretaceous formation there are in Northern 

 Europe only a few isolated fragments of Lithistidas {Q-g- in 

 the Eocene sands of Brussels) ; but on the other hand, in the 

 province of Oran, in Algeria, Pomel has discovered and de- 

 scribed a remarkably rich Miocene Lithistid fauna. Unfor- 

 tunately I have had no materials from this region at my 

 disposal ; and as Pomel's descriptions and figures relate only 

 to the external form and the canal-system, but take little 

 notice of the finer structural characters, I must for the pre- 

 sent refrain from giving an opinion upon most of the genera. 

 In general habit, however, the Lithistid fauna from the 

 Miocene of Oran appears to be at least as nearly allied to the 

 existing forms as to those of the Cretaceous formation. Among 

 ths numerous species of the genera Scytopliymia^ Pleurophymia^ 

 and Cnemaidax a closer examination may show representa- 

 tives of Corallistes, Afacandrewia, and Azorica ; on the other 

 hand, the genera Jereopsis^ Jerea^ Allomera, Meta, &c., which 

 are exceedingly numerous in individuals, seem rather to indi- 

 cate Cretaceous predecessors. To my regret I have found 

 myself compelled to ignore most of Pomel's genera in the 

 special part of this memoir, as a definitive arrangement of 

 them in the system will be possible only when their structural 

 characters have been carefully investigated. 



The following Table gives a summary representation of 

 the historical sequence of the Lithistidaj, and, at the same 

 time, some indications of the mode in which their phyletic 

 evolution may be conceived. For the present, with our imper- 

 fect knowledge both of the fossil and living Lithistidse, tlie 

 establishment of complete series of forms, or even the con- 

 struction of a genealogical tree, is no more to be thought of 

 than in the case of the Hexactinellida\ 



