216 an. f. J. noeth ox [vol. lxxvi, 



Sowerby's types are preserved in the British Museum (Natural 

 History) and typical specimens are excellently illustrated in 

 Vaughan's 'Belgian paper' (pi. iii). 



Horizon and localities. — Carboniferous Limestone (K-D) ; 

 (of the mature form, that is. the holotype, D 2 — D., ; locality, Derby- 

 shire). In this country the mature form has not been found south 

 of the Midland area, but Vaughan records its occurrence at Vise. 1 

 Remarks. — Davidson and M'Coy have included in this species 

 several forms which obviously do not belong to it, and as a result, 

 the descriptions given by both those authors are misleading. 

 M'Coy 2 describes it as having five or six cord-like ' ribs ' on each 

 lateral slope, a ' midrib ' as wide at the margin as three lateral 

 ones, and a surface covered with coarse scale-like laminae of growth. 

 He gave no figure, but he was probably referring to a form like 

 that figured by Davidson [4] pi. vii, fig. 37. In a previous work, 

 however, M'Coy stated that Sp. octoplicata had four large angular 

 ' ribs ' on each side of the mesial ridge, and a smooth surface. 3 

 None of Davidson's figures adequately depict the typical mature 

 form of this species. Those which approach nearest to it are 

 pi. vii, figs. 38-41, said to be from Sowerby's original examples. 



This uncertainty as to the precise significance of the name 

 octoplicata is probably in part to be attributed to the fact that 

 one of Sowerby's figures (fig. 4) differs considerably from, the other 

 two. There can, however, be no doubt as to which of the two 

 forms Sowerby himself regarded as the type of his species, for he 

 suggested that the specimen illustrated in fig. 4, which possessed 

 certain special characters, might prove to belong to another 

 •species. 



Of the two specimens figured by Davidson 4 from ' Lough Hill ' 

 (Sligo), 5 one, fig. 47, belongs to this species ; while the other, 

 figs. 42-44, more closely approaches Spiriferina perplicata. 



The desirability of separating this species from the Permian 

 Sp. cristata Schlotheim, has been discussed by Davidson, King, 

 L. Gc. de Koninck, and others, but owing to the uncertainty as to 

 the exact significance of either name, the opinions expressed were 

 at variance. As, however, the name cristata was originally applied 

 to a vaguely-defined Permian shell, it seems desirable to regard the 

 two species as distinct, although it is highly probable that from 

 Sp. octoplicata descended some of the Permian Spiriferinas re- 

 ferred to cristata. In the extent of the development of the 

 ventral median septum, Sp. cristata is intermediate between the 

 Carboniferous and the Liassic species. 



1 Vaughan [35] p. 45. 



2 M'Coy [21] p. 18. 3 M'Coy [20] p. 133. 



1 Davidson [4] pi. vii, figs. 42, 44, & 47. These specimens are now in the 

 Museum of Practical Geology (Geological Society Collection). That illus- 

 trated in fig. 47 bears the Register No. 5705 a, while on the same tablet is 

 that illustrated in figs. 42-44, together with a similar specimen not figured. 



5 Prof. G. A. J. Cole sug'gests that this must be a misprint for Lough Gill. 

 (In Utteris.) 



