40 



Rocks ; the following is essentially an abstract of this paper, with a slight 

 modification. 



Girvanclla was originally described in 1878 by Nicholson and Etheridge 

 jun., from the Ordovician rocks of the Girvan district, Scotland.'^' The genus 

 was established to include certain small nodular structures composed of a felted 

 mass on interlacing tubes, having a width of 10 and 18^, the cells being typi- 

 cally simple, imperforate tubes without visible internal partitions, The geno- 

 type G. p7'obLcinatica was at that time referred to the arenaceous foraminifera. 

 In 1887, BORNEMANN,^^ in describing his new genus Siphoiiema { = Girva- 

 nclla) found in the Cambrian rocks of Sardinia, suggested that this organism 

 might b-long to the calcareous algae. In 1891, Rothpletz*' noticed that some 

 of the specimens of Girvanclla which he examined were characterised by 

 dichotomous branching of the tubes ; on this account he removed the genus 

 from the RJiizopods to the calcareous algae placing it provisionally among 

 the Codiacca. Three years later A. Brown^* expressed the opinion that Gir- 

 vanella might ultimately come to be regarded as referable to the Siphoneae 

 Verticillata;. In 1898, however, A. C. Seward''* remarked that its exact 

 position in the organic world was quite uncertain, but that it might be more 

 fittingly discussed among the Schizophyta than elsewhere. Lastly in 1908, 

 RoTHPLETz'* reaffirmed his opinion that Girvanclla must be referred to the 

 Codiaccac. 



Siphoncma described by Bornemann from the Archacocyathus limestone 

 of Sardinia was shown by Hinde*^' to be congeneric with Girvanclla. Black- 



1) Geological Magazine, London. Dec. V., vol. X. 1913. p- 440 et seq. 



2) NiCHoi.soN and Etheridge: A Monograph on the Silurian Fossils of the Girv an District 

 in Airyshire. Vol. I. 1880. p. 23, pi. IX., fig. 24. 



3) Bornemann: Die Versteinerungen des Cambrischen Schichtensystems der Insel Sardi- 

 nien. Abt. I, Nova Acta d. k. Leop.-Carol. deutsch. Akad. d. Naturforscher. Bd. LI., 

 No. I. 1886. 



4) RoTHPi.F.Tz: Fossile Kalkalgen aus der Familie der Codiaceen und der Corallinen. Z. 

 d. deutsch. geol. Gesell., 1891, p. 301. 



5) A. Brown: On the Structure and Affinities of the Genus Solenopora. Geol. Mag., 

 London. Dec. IV., vol. I., p. 203. 1894. 



6) Seward: Fossil Plants. Vol. I., p. 124. 1898. 



7) Rothpletz: Ueber Algen und Hydrozoen im Silur von Gotland und Oesel. K. Svenska 

 Vetenskapsakademiens Handlinger, vol. XLIII., No. 5. 



8) Review of Bornemann's paper, cited above, by HiNoro. Geol. Mag., London. Dec. III., 

 vol. IV., p. 228. 1887. 



