380 PEOCEEDINGS OF SECTION C. 



characters which follow agree equally well, except in a single point, 

 namely, that the diameter of the tubes in Girvanella is from l-700th 

 to 1 -600th of an inch, whereas those of the present species range from 

 1 -500th to 1- 120th 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 recognise these trifling 

 differences as a basis of generic distinction." 



Subsequent to the publication of the original description of Gir- 

 vanella, Nicholson was inclined to regard Syringammina fragillisimi, 

 Brady, as the form of rhizopod m.jre closely allied to Girvanella ; {t) 

 dnd a similar tendency was shown by that author in his " Manual of 

 Palseontology " published a year later,(M) for there he refers to Gir- 

 vanella in the following words : — " The most probable view of the 

 relationships of this singular fossil is that it is an arenaceous foraminifer, 

 allied to the recent genera Syringammina and Hyperammina.^^ From 

 Rothpletz,(v) however, we learn that Nicholson, writing to that author 

 in July, 1890, expresses himself as not averse to the opinion of the 

 algal origin of Girvanella, since he had observed it, as did also Rothpletz 

 and Wethered, to show a branching habit. 



Prior to 1893 Wethered accepted the rhizopodal relationship of 

 Girvanella, but since the renewed work by Rothpletz and others, who 

 upheld its vegetable origin, he seems to have been almost won over 

 to the side of the algologists, for he then writes, (w) " I certainly think 

 that the forms which I have discovered in the Wenlock limestone seem 

 more favorable to the vegetable theory of the origin of this fossil than 

 those described in my former paper, and possibly it may be allied to 

 the calcareous algee ; more than this, however, I cannot say. Further 

 investigation may throw light on this interesting question ; but, whether 

 it be a vegetable or animal, it is certainly a very low form of life, perhaps 

 the lowest of which we have knowledge in a fossil state." 



Other Animal Groups. — The fossil erroneously referred by Miller 

 to the somewhat indefinite stromatoporoid genus Stromatocerium, 

 J. Hall, as S. rickmondense, is synonymous with Girvanella, as was 

 pointed out by Nicholson. 



Strephochetes, another synonymous genus, was regarded by Seeley 

 as " a free calcareous sponge showing in structure concentric layers 

 composed of minute twining cells." (.c) 



AlgcB. — Bornemann, (y) in 1887, described his genus Siphonema, 

 now identified with Girvanella, as an alga. 



Rothpletz {z) examined typical examples of G. prohlematica which 

 he had received from Nicholson, and concluded that they were struc- 

 turally related to the algee ; and in comparing them with SphcBro- 

 codium, a somewhat similar nodule-forming organism from the Trias 

 and Rhsetic of the Eastern Alps, remarked on the absence of sporangia 



(0 Nicholson ('88), p. 23. (u) Nicholson and Lydekker ('89), p. 128. 



(v) Rothpletz ('91). p, 302. (w) Wethered ('93), p. 246. 



(x) Seeley ('85), p. 355. (y) Bornemann ('87), pi. n. 



(z) Rothpletz ('91), p. 301, pi. xvn., figs. 8, 9. 



