part 2] SYRINGOTHYRIS A>'D SPIRIFERINA, 207 



that /S. snbconica is the direct descendant of S. laminuxa. and differs only in 

 the accentuation of the traits already adumbrated in the earlier form.' i 



But he further states that 



' A cross-section of the beak of 8. subconica reveals the character.-- of Syrin- 

 gothyris as typically developed as in S. cuspidata (Mart.) itself." 



This, however, is certainly not the ease. S. cuspidal <t and S. sub- 

 conica frequently occur together, as, for example, at Settle ; and 

 small specimens of the former hear some slight resemblance, 

 externally, to exfoliated specimens of the latter, although the dif- 

 ference between the two is at once manifest when the beaks are 

 rubbed away, and the cross-section examined. It was apparently 

 upon a small, wrongly-identified specimen of the former species 

 that Vaughan based the statement "just quoted. 



Unfortunately, from the supposed existence of the syrinx in 

 T, laminosa and the assignment of T. subconica to Syringothyris, 

 Vaughan drew certain conclusions regarding the phylogeny and 

 relationship of the two genera Spiriferina and Syringothyris :— 



'Hence, S. laminosa develops, ' phylogenetically, into a typical Syringo- 

 thyris. . . . The results obtained indicate the close relationship in Carboniferous 

 times of the two genera Spiriferina and Syringothyris. . . . The most probable 

 guess is, that Spiriferina and Syringothyris were both derived at much the 

 same time from a common ancestral group, and that they developed along- 

 different lines, but that in the earliest period of their history they possessed 

 the same essential structure.' \_Loc. citi] 



Sufficient evidence has already been adduced to show that this 

 assumption is not supported by observed facts, for T. laminosa is 

 not a Spiriferina. and that genus and Syringothyris have practi- 

 cally nothing in common. What is already known concerning the 

 evolution of Syringothyris shows that at no period of its history 

 did its ancestors show any sign of the development of the essential 

 features of Spiriferina: namely, a strongly-punctate shell-structure 

 and an elevated median septum in the pedicle-valve. Finally, 

 there are early Palaeozoic Spiriferoids with an imbricate ornamen- 

 tation of the shell and a pronounced median septum, among which 

 to look for the ancestors of Spiriferina. 



It is evident that further study of the subject was causing 

 Vaughan to modify his views, and but for his untimely death 

 would in all probability have cleared up the uncertainty which had 

 resulted from his interpretation of T. laminosa. In his last paper, 

 he speaks of two forms included under that name. One of these, 

 characteristic of the Lower Caninia Zone, he still regarded as a 

 Syringothyris, while the other, characteristic of the Upper 

 Zaplireulis Zone, with a primitive and buried syrinx and an 

 impunctate shell-strUcture, he considered to be a Spirifer, or a 

 rudimentary Syringothyris. He definitely stated that neither is 

 a Spiriferina, and added : ' In any case, it is not possible to separate 

 usefully the two forms in field-work.' 3 



, Vaughan [28] p. 384. ' 2 Vaughan [35] p. 44. 



