364 M. K. A. Zittel on Fossil Calcispongice. 
XL .—Studies on Fossil Sponges. —V. Calcispongice. 
By Karl Alfred Zittel. 
[Continued from p. 312.] 
V. Calcispongice. 
Thanks to Ernst Hackel’s brilliant monograph*, the Calci- 
spongiae, of all the sections of existing sponges, are the most 
accurately known. As regards palaeontology, however, the 
path-making work of the zoologist of Jena did not appear to 
possess the great importance which might a priori have been 
expected of it, considering the opinions previously prevalent 
upon fossil sponges. Hackel very decidedly and quite justly 
opposed the notion that the majority of the fossil sponges 
must have had a calcareous fibrous or latticed skeleton. 
u Hitherto,” he says (Bd. i. p. 341), u no fossil Calcispongice 
are known. It is true that in various collections of fossils 
there exist certain specimens with the tickets of 1 fossil Calci- 
spongiae.’ But whatever I have myself seen and had sent to 
me of such, most certainly do not belong to the Calcispongiae. 
Moreover, of all the descriptions and figures of fossil sponges , 
not a single one can he referred to a calcareous sponge. Any 
one acquainted with the living Calcispongiae will find this 
deficiency of petrified Calcispongiae perfectly natural, consider¬ 
ing their great delicacy and destructibility. We might, 
indeed, at least expect to find their microscopic calcareous 
spicules fossil in various rocks; and probably such will often 
be found by more accurate microgeological investigations. As 
yet, however, nothing of the kind has been described or 
figured.” 
When such an authority as Hackel denies the existence of 
fossil Calcispongiae so decidedly, it may seem a bold thing for 
me to say that I nevertheless refer to the Calcispongiae a con¬ 
siderable portion of the fossil sponges with a vermiform 
fibrous skeleton, denominated Vermiculata by Oscar Schmidt. 
- After the separation of the Hexactinellidae, Lithistidae, Te- 
tractinellidae, and Monactinellae, there still remains a consider¬ 
able residue of fossil sponges, distinguished by the calcareous 
and at the same time fibrous nature of their skeleton. By 
their anastomosing fibrous texture and partly also by their 
external habit, they remind one most of the existing horny 
sponges. They have indeed frequently been taken for such ; 
and it has been supposed that the horny fibres had, in course 
of time, been converted into carbonate of lime. 
* Die Kalkschwamme, eine Monographic. Berlin, 1872. 
