280 MR. E. WETHERED ON THE OCCURRENCE OF 



Roacli Bed. — A mass of shell-dobris ; the structure is often well 

 preserved in the fragments ; no oolitic spherules appeared. 



In none of the slides from the Portland Beds was Girvanella de- 

 tected. As to the origin of their oolitic spherules, it is impossible 

 to express any positive opinion, on account of the alteration they 

 have undergone by crystallization. 



The New Species. 



To make distinctions between organisms such as the GirvaneU(f 

 is a task of considerable difficulty, but to do so is a matter of 

 necessity. 



I. Girvanella incrustans, PL XI. figs. 1 a, h. — Occurs onlj^ in the 

 Carboniferous Limestone at Clifton, in spherules as large as 3 millim. 

 in diameter. When cut in section, the organism is seen to consist 

 of a dense crust of very tortuous minute tubuli, which measure 

 •01 millim. in diameter. They are arranged in rude layers, formed 

 around a centre, which is usually represented by calcite into which 

 the original nucleus has probably l)een converted. 



Girvanella incriistans, variety Lucii (fig. 3), is very similar to 

 G. incriistans ; but so far I have i]ot found the tubuli to occur in 

 layers, but as an irregular mass incrusting foreign objects. I have 

 found G. incrustans only as spherules ; but the variet}' Lucii., as 

 represented in the figure, is not a spherule. The differences between 

 the two varieties are slight ; but as one occurs in the Carboniferous 

 Limestone and the other in the Inferior Oolite, I think it better to 

 give the varietal name of Lucii to the latter. 



II. Girvanella Lucii, PI. XI. figs. 2 a, 6, c. — This species is confined 

 to the Carboniferous Limestone, and has been found at Clifton and 

 Tortworth Park in Gloucestershire. The test consists of a tortuous 

 tube, with clearly defined walls of dark granular structure, and 

 measuring '02 millim. in diameter. In some instances the tubes 

 occur in irregular loose aggregations, at other times adhering to 

 foreign objects, as represented in fig. 2 6, when a small nodule or 

 granule results. In some instances G. Lucii assumes a more or 

 less spherical form, and the inner tubes are surrounded by a con- 

 centric structure. Whether in this case the central tubes are 

 nuclei and the concentric arrangement concretionary or organic 

 is doubtful, and worthy of consideration by future observers. I 

 have not as yet been successful in discovering a primordial chamber : 

 but, seeing that in the living Foraminifer LLiperammina vagans. 

 which G. Lucii resembles, the primordial chamber is " almost inva- 

 riably wanting " *, it is not surprising that, in the fossil state, it 

 should be still less easily detected. 



III. Girvanella mimita, PL XI. figs. 6 a, b. — The test consists of a 

 short minute tube, Avhich measures "007 millim. in diameter. These 

 tubes are enclosed by a thin dark granular wall, and occur in the 

 centre of oolitic spherules (fig. G a), or in aggregations or around 

 some foreign object (fig. 6 6). 



* ' Challenger ' Report, Zoology, vol. ix. p. 260. 



