194 BRITISH JURASSIC SPONGES. 
corresponding Jurassic strata of France, Germany, and Switzerland; but there are 
many other species closely allied to Continental forms. It is a noticeable fact 
that, as first mentioned by Prof. Sollas,’ some of the species and nearly all the 
genera of Hexactinellid and Lithistid sponges present in the Inferior Oolite of 
Dorsetshire are similar to those which in Wiirtemberg and in the Swiss Jura appear 
in the distinctly higher horizon of the Upper, or White, Jura. Thus the genera 
Tremadictyon, Verrucocelia, Stawroderma, Platychonia, and Melonella, together 
with Craticularia clathrata, Goldf., sp., and C. foliata, Quenstedt, sp., all recur 
in the Upper Jura in Germany. The Sponge-bed in the Inferior Oolite at Burton 
Bradstock, may well be compared in the number, variety, and mineral condition of 
its siliceous sponges with one of the zones of Spongiten-Kalk in the White Jura 
of Wirtemberg. There is no sponge-bed in the corresponding middle Dogger in 
Germany to compare with that in our Inferior Oolite; and, on the other hand, 
there are no beds of Siliceous Hexactinellid sponges in our Corallian and Portland 
strata at all analogous to the sponge-zones in the Upper Jura of Germany. 
The great abundance of Calcisponges*forms the characteristic feature of the 
sponge fauna of our Jurassic rocks. In the Inferior Oolite the number of species 
exceeds that of the siliceous forms; in the Great Oolite there are fourteen species 
and no representative of siliceous sponges, and in the Corallian series there are 
seven species, as compared with a single species of siliceous sponges. ‘Through- 
out the different divisions, the Calcisponges are fairly well preserved, their mineral 
structures are rarely altered, and in most of them the spicular character of the 
fibres can be recognised in thin sections, whilst in some the smallest spicules have 
been preserved intact. 
In conclusion, I wish to acknowledge the generous assistance which I have 
received in the preparation of this part of the monograph. Mr. R. F. Tomes, of 
Evesham, Rev. G. F. Whidborne, Mr. F. Longe, of Cheltenham, and Mr. H. 
Wethered have supplied me with numerous specimens from the Pea-grit and the 
other beds of the Inferior Oolite. To my friend Mr. HE. A. Walford, of Banbury, 
IT am specially indebted for the beautiful little Calcisponges from the Middle Lias, 
and for the extraordinary variety and abundance of sponges which he obtained 
from the Inferior Oolite beds at Shipton Gorge. For the Yorkshire examples of 
Corallian sponges I am further indebted to the untiring energy and zeal of Mr. 8. 
Chadwick, who has repeatedly sent me specimens and obtained for me the 
required information as to their occurrence. I also wish very heartily to thank 
Prof. T. McKenny Hughes for the opportunity of studying the unrivalled 
collection of Great Oolite Calcisponges in the Woodwardian Museum at 
Cambridge, and also to Mr. H. M. Platnauer my best thanks are due for the loan 
of valuable specimens from the Museum at York. 
1 «Quart. Journ. Geol. Soe.,’ vol. xxxix, 1883, p. 551. 
