72 Proceedings of the Royal Society of Victoria. 



Salter's original specimen was beyond doubt an example of 

 Teiragraptus bryonoides or T. bigshyi, and that Salter then con- 

 fused an English species with it. It seems to me, however, that 

 Professor Hall has by no means proved that Salter made a 

 mistake, for he apparently did not see Salter's species — at any 

 rate, he does not figure it. The Skiddaw slates and the Quebec 

 group are on the same horizon, so there is nothing improbable in 

 Salter's species being found in England. From this it would 

 appear that I), gibberuliis must be relegated to synonymy, for it 

 does not s'^em separable from D. cadnceus. 



Mr. R. Etheridge, jun., in his papei- on the Victorian grapto- 

 lites,* when dealing with T. bryonoides., accepts the decision that 

 D. Ciidi/cens is referable to that species. At the same time he 

 suggests the advisability of keeping Salter's name for a variety 

 which he recognises as constant in its characters, and as agreeing 

 with Salter's figures and descriptions. 



In a previous paperf I tacitly accepted the identity of 

 Tetragraptiis bigsbyi and Didyniograptns cadnceus, and, as Salter 

 had clear priority, called the species T. cadnceus, in this following 

 Herrmann's lead. At the same time I kept T. bryonoides, Hall, 

 (= T. serra, Brong.) distinct. I now regard Salter's species as 

 a clear Didymograptus. I examined a very large number, 

 probably some thousands, in the field during my residence in 

 Castlemaine, where it occurs in pi-ofusion, and gathered every 

 specimen that appeai-ed to point to its being a Teiragraptus. These 

 I have repeatedly examined carefully and without any hesita- 

 tion refer all the forms with more than two arms to T. serra, 

 Brong. The distinguishing points are just those that Professor 

 ^Nicholson drew attention to when describing D. gibberulus. The 

 distinction is that the first developed hydrothecte of JJ. cadnceus 

 are as large as any subsequently formed, and that their long axis 

 agrees with that of the sicula ; whereas in T. serra ( = T. bryon- 

 oides) they are invariably much smaller and diverge greatly from 

 the sicular axis usual in Didymograpti. The result of this is 

 that the stipe of the latter species is much conti'acted or nar- 

 rowed in tlie sicular region, while in the former species it practi- 

 cally reaches its full width at once. 



• Annals and Ma;;-. Nat. Hist., 4, iv. f Prooeeflings Royal Soc. Victoria, 1894. 



