384 PROF. S. H. REYNOLDS AND DE. A. VAUGHAN ON [Aug. 191 I, 



Comparison with Syringotliyris subconica (Mart.), 

 from the D Zone. — S. subconica is so similar to S. laminosa 

 that its specific separation has been viewed with scepticism. 

 There seems, indeed, to be no reasonable doubt that S. subconica 

 is the direct descendant of IS. laminosa, and differs only in the 

 accentuation of traits already adumbrated in the earlier form. 



A cross-section of the beak of S. subconica reveals the characters 

 of Syringotliyris as typically developed as in S. cuspidata (Mart.) 

 itself. Hence S. laminosa develops, phylogenetically. into a 

 typical Syringotliyris. 



The problem consequently seemed to have been satisfactorily 

 solved, and the separation of Spiriferina from Syringotliyris was 

 reduced to the rubbing down of the beak : — 



If the mesial septum appears at once, without a trace of syrinx : — 



Spiriferina. 

 If the mesial septum is delayed, and there is at least a primitive syrinx: — 



Syringothpis. 



Comparison with Carboniferous l Spiriferinas ' has reopened the 

 problem. This investigation is as yet incomplete, but the results 

 obtained indicate the close relationship in Carboniferous time of 

 the two genera Spiriferina and Syringotliyris. For example : — 



In Spiriferina octoplicata (J. de C. Sow.), which is common in 

 the D Zone, the appearance of the mesial septum is retarded, and 

 there are Syringothyroid characters in the cross-section. 



In Spiriferina peracuta de Kon., common in early Z in Belgium, 

 the mesial septum is a mere ridge. (The cross-section has not yet 

 been studied.) 



The most probable guess is, that Spiriferina and Syringotliyris 

 were both derived, at much the same time, from a common ancestral 

 group, and that they developed on different lines, but that, in the 

 earliest period of their history, they possessed the same essential 

 structure. 



The figured specimen, from y of Burrington, shows the syrinx 

 on the rubbed-dowc beak. 



History. — An early mutation occurs at /3 (see below) ; S. sub- 

 conica is the D mutation. 



Spiriferina cf. octoplicata (J. de C. Sow.), Vaughan, 'Bristol 

 Paper' pi. xxvi, fig. 6. 



Occurrence. — K and (3 of the South-Western Province; rare 

 at Burrington in K . 



The small shells included under this head, from the South- 

 western Province, probably comprise two species : — 



(1) An early mutation of Syringotliyris laminosa, discussed 

 above. Compare figure of young form, de Kon. op. cit. 

 pi. xxii, figs. 49-50. 



This completes the history of the gens S. laminosa in the 

 Avonian. 



