Vol. 68.] SUCCESSION IN THE NOETH-WEST OF ENGLAND. 571 



Spieifee furcattjs M'Coy.^ 



This small Spirifer, which occurs abundantly near the summit of 

 the Atliy ris-glahristria Zone on Meathop Fell, in Docker Beck, and 

 elsewhere, bears a very close resemblance to M'Coy's figure. It 

 is a somewhat variable form, and does not always show the 

 bifurcation of the ribs clearly at the anterior portion of the shell. 

 In some specimens, apparently belonging to this species, the ribs 

 are more numerous and the bifurcation takes place nearer the 

 posterior margin. 



This form approximates occasionally to Sp. duplicicostatus, 

 under which name Davidson includes M'Coy's species ; but, on 

 the whole, it differs from the typical examples of that species in 

 the following points : — 



1. The subquadrate form of the shell. 



2. The less numerous and coarser ribs. In the pedicle-valve there is a 



somewhat marked bifurcation about the third rib from the sinus. 



3. The narrower character of the mesial fold, especially towards the anterior 



border, giving a more parallel and less divergent appearance to the 

 ribbing. 



4. The well-marked growth-lines towards the anterior margin of the shell: 



these are clearly shown in M'Coy's figure. 



Horizon and localities. — Very characteristic of the band 

 near the summit of the Athyris-glabristria Zone. It is doubtful 

 whether it occurs outside this band in the JSTorth-Western Province. 

 A few specimens met with at a slightly lower horizon in the 

 Haven stonedale District should perhaps be assigned to this form. 

 Meathop Pell, Arnside District; Beck Head, Grange District; 

 EUiscales, Furness District. 



Seminijla geegaeia (M'Coy). (Pi. LI, fig. 5.) 



The typical form of the Athyrid selected for the zonal index of 

 the upper portion of the Athyris-glahristria Zone in the Shap and 

 Eavenstonedale Districts is shown in PL LI, fig. 5. It appears to be 

 identical with Isi'-CoY^ '■ Atrypa gregcma,' figured in his 'Carbo- 

 niferous Limestone Fossils of Ireland ' pi. xxii, fig. 18. With regard 

 to its true generic affinities, very little information can be obtained 

 from the occurrences of this species in the North-Western Province, 

 as the specimens are there invariably dolomitized. Dr. Yaughan 

 informs me that the species is probably a Cryptonella, but it cannot 

 be definitely assigned to its proper genus, until better specimens, 

 showing internal characters, are obtainable. 



Seminula aff. ficoidea Yaughan. (PL LI, fig. 6.) 



This form bears a close general resemblance to Dr. Yaughan's 

 figure of S. ficoidea.^ It appears, however, to differ from that 

 species by its more swollen character ; by its greater length of 



1 See F. M'Coy, ' Syn. Carb. Limest. Foss. Ireland ' 1844, pi, xxii, fig. 12 

 & p. 181. 



-' Proc. Bristol Nat. Soc n. s. vol. x (1903) pi. ii, fig. 1. 



