218 Dit. r. j. noeth ox [vol. IxxvL 



In the brachial valve there are, on each side of the angular fold, 

 three lateral costs; ; the first of these is nearly as large as the fold, 

 but the others decrease rapidly in size. In the pedicle- valve, in- 

 cluding those bounding the sinus, there are three costai on each 

 lateral slope. The fold, the sinus, and the eostaj are sharply 

 angular, and the latter are separated by deep angular furrows about 

 as wide as the costie. The surface of both valves, except the 

 cardinal area, is covered by strongly -imbricating lamellae, especially 

 distinct anteriorly. The shell-substance is strongly and coarsely 

 punctate. 



Nothing is known of the internal structures, beyond the fact 

 that there is a median septum in the pedicle-valve, like that in 

 Spiriferina octoplicata. 



The dimensions of an average specimen are as follows : width 

 along the hinge-line, 14 mm. ; length of brachial valve, 9 mm. 



Remarks. — Small immature specimens have a lower area, and 

 are less tumid ; but the small number of prominent costa;, the 

 deeply-serrated anterior margin, and the strong lamellar ornamenta- 

 tion enable them to be readily identified : although, since the outer 

 lateral costa? commence at some little distance from the beak, 

 there are, in young shells, only two lateral costa- 1 on each side, and 

 these are somewhat less angular than in the adult. 



Under some conditions of preservation the external shell-layers 

 are lost, and the surface appears to be smooth ; the pimctse are 

 then very distinct. The immature form is well illustrated by a 

 small specimen B 20370, from Grwyn, Llanfair (Anglesey), in the 

 Geological Department of the British Museum (Natural History), 

 and by some of Davidson's figures, as. for instance, [4] pi. lii, 

 figs. 14 & 15. 



Sp. qvincpueloba of M'Coy was, in all probability, a small, but 

 not typical, example of this species. 



Sp. insculpta may be distinguished from Sp. octoplicata by the 

 small number of the costa and the deeper furrows separating them; 

 by the more uniform distribution of a strong lamellar ornament ; 

 and by its general shape. The hinge-line of insculpta is rela- 

 tively shorter than that of octoplicata, so that in the former 

 species the shell tends to be rotund, while in the latter it is dis- 

 tinctly elongated. 



Horizons and localities. — Upper Avonian (especially D.,) in 

 the Midlands and Yorkshire, as, for example, Parkhill, Wetton, 

 Settle. It is last recorded from the Upper JPosidonomya Beds of 

 Loughshinny, where it is represented by a typical specimen figured 

 by Vaughan. 1 None of the Lower Avonian Spiriferina; from the 

 South-Western Province appear to belong to this species ; but the 

 name has been applied to small highly-plicated Spirit erids occurring 

 in the Devonian rocks. 2 In these, howeA r er, the shell-substance is- 

 impunctate, and they are, in all probability, representatives of the 



1 Vaughan [24] pi. 1, %. 9. 



2 G. F. Whidborne, ' A Monograph of the Devonian Fossils of the South of 

 England' Pal. Soc. vol. ii (1892 97) pp. 109-10. 



