GIRVANELLA IN OOLITIC EOCKS. 281 



lY. Girvanella intermedia, PI. XI. fig. 7. — The test consists of a 

 vermiform tortuous tube, which grows in nodular masses. The tubes 

 measure '01 millim. in diameter, and have well-defined thin walls. 

 I have not as yet found this form adherent. 



In concluding this paper I should like to say, first, that it has 

 been my object to produce evidence that oolitic structure is not 

 always of concretionary origin. That it is all organic I am not pre- 

 pared to maintain, but it may be. 



DESCEIPTION OF PLATE XI. 



Fig. 1 a. Spherule of Girvanella incricstans ; x 28 diam. Seen in section. 

 From the " New-Eoad Oolite," Middle Carboniferous Limestone, 

 Clifton. 



Fig. 1 b. Portion of fig. la; X 70 diam. Showing the tubules of Girvanella 

 incrustans. 



Fig. 2«. Girvanella Bucii occurring as an aggregation; X 70 diara. " New- 

 Koad Oolite," Middle Carbonifei'ous Limestone, Clifton. 



Fig. 2 b. The tubules of Girvanella JDucii attached to foreign objects, which 

 act as nuclei for the formation of an oolitic granule or spherule. 

 X 52 diam. 



Fig. 2 c. The tubules of Girvanella Ducii in the centre of an oolitic granule, 

 and surrounded by a radiate and concentric structure of doubtful 

 origin, but probably organic. X 68 diam. 



Fig. 3. Girvanella pisolitica, coiling upon itself, with what is suggestive of the 

 primordial chamber at A. 



Fig. 4. Portion of an oolitic spherule from the Upper Freestones of the 

 Inferior Oolite, from near Chedworth. The spherule is passing 

 into the granular-crystalline condition. X 50 diam. 



Fig. 5. Gh-vanella i^icrustans, variety Lncii, attached to a foreign object. From 

 the same beds as fig. 4. X 70 diam. 



Fig. 6 a. An oolitic spherule from the Coralline Oolite at EadcIifF Poiut, near 

 Weymouth, with the tests of Girvanella minuta in the centre, 

 surrounded by a concentric ai-rangement of doubtful origin, but 

 probably organic, X 70 diam. 



Fig. C b. Girvanella minuta, attached to a foreign object, which has been con- 

 verted into calcite. The latter acts as a nucleus, and an oolitic 

 granule results. On the left-hand side, and on the outer edge of 

 the right, the tubuli have passed into the granidar crystalline con- 

 dition. X 70 diam. From the Coralline Oolite, Wyke, near 

 Weymouth. Only a portion of the granule is represented. 



Fig. 7. Girvanella intermedia forming an oolitic spherule. Coralline Oolite, 

 Wyke, shore near Weymouth. X 70 diam. Around the edge of 

 the granule the tubules have passed into the granular crystalline 

 condition. 



Fig. 8. A crystalline oolitic spherule, showing perfect concentric arrangement 

 around a nucleus which has become converted into calcite. 

 Coralline Oolite, Eadcliif Point, near Weymouth. X 70 diam. 



[Most of the figures are represented imbedded in the limestone.] 



Discussion. 



The President remarked on the importance of investigating the 

 (juestion whether these appearances arc organic or not. We should 

 take warning from Kozoon as to possible differences of opinion in the 



f2 



