62 



ACANTHODES MITCHELLI. 



of the entire length. The cranial bones are gracefully sculptured 

 with deep sinuous lines. The orbit occupies an advanced position, 

 and is embraced by a set of the singular orbital plates first noticed 

 and described by Ferd. Komer as characteristic of the genus 

 Acanthodes. The branchial apparatus also corresponds with that ot 

 the other members of the genus. The outline of the body is re- 

 markably graceful. It is fusiform anteriorly, and tapers gradually 

 posteriorly to the base of the caudal fin. The latter organ is highly 

 heterocercal, although the upper member is not so much extended 

 as the corresponding part in the genus Climatius, All the 

 other fins are supported by stiff spines. The pectoral spines are 

 long and curved, the other fin spines are more slender and straight. 

 The ventral fins are situated nearer to the anal than to the pectoral 

 fins, and the dorsal spine is slightly nearer the tail than the anal 

 fin. The species differs from its congeners in having the cranial 

 bones more deeply sculptured, and in the form and position of the 

 fin spines. It is most nearly allied to Acanthodes Peachi, but it 

 differs from this species in the form of the body, in having the 

 pectoral spines more curved, and the other spines straight, and in 

 the more remote position of the dorsal fin. 



Locality. — The deposit which has yielded this and the following 

 interesting additions to the Fauna of the Old Ked Sandstone of Scot- 

 land, is situated on the south-east bank of the Pow burn about half 

 a mile south-west of the Farnell Ration on the Scottish North-Eastern 

 Railway. It is described by Mr. Powrie as consisting mostly of 

 fine grayish argillaceous shales, the lower beds splitting into fine 

 laminge nearly as thin as writing paper, and, when first opened, of 

 a delicate cream colour. In a subsequent part of the paper the 

 author says, " no painting could equal the beautiful appearance 

 " some of the smaller fishes exhibit when the little slab in which 

 " they have been entombed is first opened up, and still damp." 

 The Eev. Henry Brewster of Farnell was the first to discover the 

 fossiliferous character of these shales, but the Rev. Hugh Mitchell of 

 Craig first ascertained the association of fishes with the organisms 

 previously discovered, and called attention to the subject in a paper 

 he communicated to the Geological Section of the British Associa- 

 tion at the Aberdeen meeting in 1859. Through the liberality of 

 Lord Southesk, to whom the quarry belongs, every facility has 

 been afforded for exploring its contents, and the zealous labours of 

 Mr. Powrie and the Rev. Henry Brewster have added considerably 

 to the stock of materials collected by the Rev. Hugh Mitchell. I am 



