W. J. 8oUas — On Greensand Foranivnifera and Sponges. 273 



in section, is preserved, into whicli canals may be seen opening on 

 all sides from the surromiding matrix. 



On a review of the evidence I have just brought forward, few, I 

 think, will be disposed to deny to a large proportion of the Copro- 

 lites, whose nature has for so long remained doubtful, a spongeous 

 origin ; their constancy in sponge form, the characters and arrange- 

 ment of their well-marked oscules, their spicules, and the general 

 connexion of coprolitic deposition with pre-existing animal matter, 

 seem to force upon us the conclusion that to a large extent they owe 

 their origin to sponges. The task now remains to determine the 

 families and genera of recent sponges to which these fossils are most 

 nearly allied ; this will be a matter for laborious research, but so fixr 

 as my investigations have yet carried me, I feel myself justified in 

 pointing to the families JEsperiadcB (Dr. J. E. Gray) and Tethjadcs 

 (Gray) as those to which a number of these forms approach most 

 nearly ; while others hold most undoubted relations to the Ifalichon- 

 dridce (Gray). 



In connexion with this subject, I may mention that spicules of 

 Geodidce, Tethyadce, and other genera have already been definitely 

 determined from the Upper Greensand of Blackdown.' 



Besides this comparison of the Greensand fossil sponges with 

 living forms, there also remains to be accomplished their correlation 

 with the Coprolites of other deposits, a work only just entered upon ; 

 it is interesting to nol e, however, that so lo wdown as the Lower Silurian 

 of Canada, Coprolites have been found, one specimen of which, un- 

 usually rich in organic matter, contained small cylindrical bodies 

 closely resembling the spicula of Sponges.^ 



Travelling upwards in the stratigraphical series, we find that as 

 the close ot the Gaidt is characterized by the occurrence of a large 

 number of phosiDliatic nodules or Coprolites, so the close of the 

 Chalk is distinguished by an abundance of peculiar siliceous nodules 

 or Flints. There is, moreover, between these Flints and Coprolites so 

 decided a parallelism, that in speaking of the Coprolites as the Flints 

 of the Gault, one can scarcely be said to be indulging in metaphor. 

 Both have been placed in the category of concretions, both alike have 

 been formed by the mineralization of highly decomposable organic 

 matter. It has been shown in both cases, that this animal matter 

 has been largely derived from sponges ; the Foraminifera and 

 Xanthidia so characteristic of the Flints are found also .in the 

 Coprolites ; and the Ventriculites which so generally accompany the 

 former are not absent from the latter, since I have recently shown 

 that several species of Ventriculites and Cephalites are far from 

 uncommon in our deposit, and, indeed, that it is characterized by 

 the very same species which appear later on in the Chalk strata 

 (V. tesselatiis, mammillaris, cavatus, quincuncialis ; Cephalites guttatits, 

 capitatus, etc., etc.).^ 



' Fossil sponge spicules. Ann. Mag. Xat. Hist., ser. 4, vol. yi. p. 192, 1870, and 

 Devon Assoc. Advt. Science, Lit., and Art, 26tli July, 1870. 

 - Geological Survey of Canada, loc. cit. 

 3 Quart. Journ. Geol. Soc, vol. xxix., p. 63. 



VOL. X. NO. CVIII. 18 1 



