2& WATSON & Day, Xotes on some Palceozoic Fishes. 



to the Upper Old Red, and, as Coccosteics occurs in them, 

 it seems probable that they belong to a low horizon in 

 that group. This view is supported by the occurrence of 

 Acanthodians and CJieirolepis, types which in England 

 occur in the Middle Old Red. CJieirolepis has, however, 

 been found in the Upper Old Red in Shetland associated 

 with Asterolepis, which form itself does descend into the 

 Middle Old Red, where it is found associated with 

 " Dipterus valenciennesi' ' 4 above the Gloup in Deerness. 

 BotJiriotepis, however, does not occur below the Scaat 

 Craig beds, although Mr. Taylor, of Lhanbryde, has found 

 it in association with Asterolepis at Whitemire. 



The marked resemblance between Eusthenopteron and 

 TristicJwpteriis also supports this determination of the 

 age, and we intend to regard the Scaumenac Beds as 

 practically contemporaneous with those of Nairn. 



Dipterus valcucieuncsi, Sedg. & Murch. 

 So far as we know no figure representing the arrange- 

 ment of the plates of the head of this " species," the 

 original of which was found in the Stromness horizon, 

 has yet been published. There is in Manchester a single 

 specimen collected by one of us at the Achanarras Quarry, 

 which shows quite clearly the structure of the roof of 

 the skull in this "species." This structure will be more 

 clearly understood from the figures. [PL L, Fig. I ; 

 Text-fig. 8 A) than from any description. The significant 

 features are, the occurrence of a transverse series of three 

 plates on the extreme back of the skull similar to the 

 post-parietal and tabulars of a Rhipidistian, the anterior 

 ed«;es of which articulate with another transverse row 

 also mainly composed of three plates. The middle one of 



4 We are not convinced of the identity of these fish with the typical 

 valenciennesi of Banniskirk, although there are no obvious definable 

 differences. 





