375 
M. K. A. Zittel on Fossil Calcispongice. 
their form exactly. All other characters, derived from the 
external form, the structure, and the canal-system, prove insuf¬ 
ficient for the establishment and especially for the sharp dis¬ 
crimination of natural groups. In the special part I have 
therefore enumerated the genera in the sequence in which 
they can best be arranged in accordance with the totality of 
their characters which are accessible to observation. 
Occurrence , Distribution in Time , and Pedigree. —In oppo¬ 
sition to the Hexactinellidse and Lithistidas, the Pharetrones 
occur associated together and in considerable numbers only in 
deposits of littoral origin, and most frequently in marly and 
sandy rocks, usually mingled with numerous Gastropoda, 
Pelecypoda, Brachiopoda, Bryozoa, and Echinodermata. The 
most ancient calcareous sponges which I have been able to 
examine are derived from the Devonian Stringocephalus- 
limestone of Vilmar in Nassau, a locality celebrated for its 
wealth of w T ell-preserved Gastropods and Bivalves. These 
belong to the rich genus Peronella. According to an oral 
communication from Prof, de Koninck numerous undescribed 
forms are found in the Carboniferous Limestone of Tournay 
in Belgium. Among the sponges of the Dyas described by 
Geinitz and King, Eudea tubercidata , King, may belong to 
Corynella ; but most of the others are very doubtful, and some 
of them certainly of inorganic origin. 
The extra-Alpine Trias has furnished a genus of Phare¬ 
trones ( Corynella) only in Silesia; but, on the other hand, 
there is in the Alps near St. Cassian, and in the Seeland Alp 
near Schluderbach, the first rich Calcispongian fauna, in which 
thirteen genera with numerous species have been discovered. 
These deposits bear the most decided stamp of littoral forma¬ 
tions, and are filled with that characteristic pygmy fauna 
which, according to Fuchs, lived in the fields of Laminarias 
of that epoch. The genera Eudea , Peronella , Corynella , Ver- 
ticilliteSj Colospongia , Stellispongia , Leiospongia , Pharetro- 
spongia , &c. already represent the most important modifica¬ 
tions which occur in the structure and external appearance of 
the Pharetrones in general. 
From the Rhsetics of the Bavarian Alps I am acquainted 
with some badly preserved and in part siiicified Calcispongias, 
which, however, cannot be accurately determined. The Lias 
appears to have been very unfavourable to the development of 
sponges; it has hitherto furnished only isolated siliceous 
spicules, but no coherent skeletons of either siliceous or calca¬ 
reous sponges. 
From the Inferior Oolite of Bayeux and Port-en-Bessin, in 
Calvados, Michelin and D’Orbigny mention numerous sponges, 
