GIRVANELLA. IN OOLITIC EOCKS. 275 



The organisms attach themselves to a foreign substance which 

 finally becomes a nucleus in the centre of a mass of GirvaneVa 

 tubules, and a spherule results, the exact shape depending upon the 

 form of the nucleus. I am not sure that I should not be justified in 

 making a new genus out of some forms which occur in the Pea- 

 Grit. In some spherules the tubes have the appearance of branching, 

 a feature -which is absent in what may be considered the typical 

 Girvanella, Professor Nicholson remarks * on what he considers to 

 be a close comparison between Girvanella and the ' Challenger ' 

 Foraminifer, SijringammmafragiUssinia (' Challenger' Reports, vol. ix. 

 p. 242, woodcut, fig. 9). In describing this organism Dr. Brady 

 fc^ays (loc. cit.) : — " Test free ; consisting of a rounded mass of 

 branching, inosculating tubes, radiating from a common centre, and 

 arranged in more or less distinct concentric tiers or layers, which 

 are marked by the formation at intervals of a network of lateral 

 branches." 



Dr. Brady, however, appears to take a different view from that of 

 Professor Nicholson, for under the head of Hyperammina vacjans he 

 refers to Girvanella ■prohhmatica -^ and, after quoting the description 

 originally given by Professor Nicholson and Mr. Etheridge, jun., 

 remarks {op. cit. p. 261): — "This description applies in every particular 

 to such specimens of Hyjperammina vacjans as are represented in 

 figs. 7 and 8 ; and the specific characters which follow agree equally 

 well, except in a single point, namely, that the diameter of the tubes 

 in Girvanella is from y-Jpyth to 73-^0^'^ ^^ ^^ inch, whereas those of 

 the present species range from -T^-J-oth to y^oth of an inch. Some 

 latitude must be allowed in estimating the characters of a minute 

 fossil belonging to so very remote an age; but it seems scarcely 

 worth while to recognize these trifling differences as a basis of generie 

 distinction." Now, assuming that the ^enus Girvanella is rightly 

 referred to the Poraminifera, some forms which I have included 

 under the head of Girvanella pisolitica appear to correspond with 

 Syrhif/ammina fragilissima ; but on the other hand the Carboniferous 

 forms I have mentioned, and some to be referred to further on, are 

 allied to Hyperammina vagans. In reference to that organism Dr. 

 Brady further remarks (loc. ci^. p. 260) that it occurs "spreading in 

 irregular tortuous lines over the surface of shells or stones, or, in the 

 absence of foreign bodies, growing coiled upon itself in irregular 

 masses." The coiling upon itself is also a feature in Girvanell-i 

 pisolitica., as shown in fig. 3, where apparently we get the primordial 

 chamber at A. 



Passing now to the beds of the Inferior Oolite which follow the 

 Pea-Grit series, we come to the Lower Freestones. There is a con- 

 siderable amount of calcite present, and some of the spherules are 

 granular, without any concentric or other structure. At Bull 

 Cross, near Stroud, the beds appear not to have undergone molecular 

 change to suck an extent as at Leckhampton, near Cheltenham ; 

 and in my prepai-ed section from these beds I have several spherules 

 showing the structure of G. ^risolitica. 



■^ Geol. Mag. dec. iii. vol. v. p. 23 (1888). 



