54 DK. G. J. HINDE OX A NEW GENUS OF SILICEOUS SPONGES 



4. On a NEW Genus of Siliceous Sponges from the LowePv Calca- 

 reous Grit of Yorkshire. By George Jennings Hinde, Ph.D., 

 r.G.S. (Eead November 20," ] 889.) 



[Plate VI.] 



TfEARLT forty years since*, Dr. H. C. Sorby, P.R.S., communi- 

 cated to this Society a paper on the microscopical structure of 

 the Calcareous Grit of the Yorkshire coast, in which reference 

 was made more particularly to the nature of certain microscopic 

 reniform bodies with which, the rock in places was largely filled. 

 In mineral constitution some of these bodies were of calcite, others 

 of chalcedonic silica, whilst in others both these minerals were 

 present, and the question as to their origiijai constitution was 

 decided by Dr. Sorby in favour of the calcite, since it was 

 thought extremely improbable that, if originally of silica, this 

 material would have been dissolved and replaced by calcite, whereas 

 the substitution of silica in place of calcite was a well-known 

 l^henomenon. The definite form and outline of these bodies left no 

 doubt that they were of organic origin, and Dr. Sorby recognized 

 their resemblance to the small siliceous globules which form an 

 ourer crust to many existing sponges, but rejected this view on the 

 ground of their supposed calcareous nature, and he finally concluded 

 that they were small shells, possibly Poraminiteral, in whose interior 

 calcareous or siliceous materials had been infilti'ated, in the same 

 manner as in the chambers of the Ammonites occurring in the same 

 rock. 



Subsequently, in 1876, Prof. J. F. Blake f, P.G.S., discovered 

 similar minute bodies in rocks of nearly the same age in Doiset- 

 shire and Wiltshire, and noticed that some of them were hollows 

 enclosed by thin crusts or shells, which dissolved in acid, and further 

 that their surfaces were ornamented by regular rows of small pits, 

 which were supposed to indicate minute perforations in the shell. 

 On these grounds they were described as peculiar forms of Porami- 

 nifera, and named Renulina Sorby ana. In an incidental reference 

 in a later J paper, Prof. Blake hints at the possibility that they may 

 have been originallj^ siliceous. 



Mr. W. H. Hudleston §, P'.E.S., likewise refers to these same reni- 

 form bodies in treating of the generally siliceous character of the 

 Coral Pag at North Grimston, in Yorkshire, and adopts the view 

 that they were siliceous spicules, similar to those forming the outer 

 layer of the recent sponge, Geodia arahica. In this case the author 



* Quart. Journ. Geol. Soc. vol. -vii. (1851), pp. 1-6. See also 'Proceedings 

 of the Geological and Polytechnic Society of lorkshire,' June 5, 1851, vol iii 

 pp. 197-206, pi. iv. 



t Monthly Microscopical Journal, toI. xv, pp. 262-264. 



+ Proc. Geologists' Assoc, vol. v. (1877), p. Z66. 



§ lb. vol. v. p. 443. 



