Dr Traqiiair on the, Genus Gyracanthus {Agassiz). 103 



form, with very oblique and entirely smooth or non-tubercu- 

 latecl ridges, which ridges also bifurcate, and even trifurcate, 

 in a very remarkable manner, as shown in the figure. If this 

 description is correct, ^ G. nohilis is even more distinct from 

 G. almvicensis than from any other. 



One remarkable feature in these spines as occurring at 

 Borough Lee is the small amount of apical wearing to which 

 they have for the most part been subjected. Even the 

 extreme point, only a little blunted and polished, is some- 

 times present in large specimens, and in many others com- 

 paratively little of the extremity has been lost by that 

 process which has reduced some of the large Gyracanthus- 

 spines from Northumberland and Staffordshire to mere 

 stumps. It has been noted that this wearing process has 

 obliquely truncated tlie l^orthumbrian specimens in their 

 anterior aspect ; but in those from Borough Lee evidence of 

 wearing is sometimes found on the posterior aspect as well. 

 These circumstances would lead us to infer some difference 

 either in the habitat or the habits of the species in question. 



Gyracanthus Yo ungii — Traqu air. 



Gyracanthus Youngii (Traq.), Geol. Mag., dec. ii,, vol. x., 1883, p. 543. 



Occurring also at Borough Lee, but found likewise in many 

 other localities on the horizon of the Scottish " Edge " Coal 

 or Middle Carboniferous Limestone series, is a remarkably 

 distinct species of Gyracanthus, to which I have given the 

 name G. Youngii, in honour of my friend Mr John Young, 

 of the Hunterian Museum, Glasgow, who has done so much 

 for the elucidation of the palaeontology of the west of Scot- 

 land. The finest specimens I have seen are in the collection 

 of Mr E. Craig, Beath, Ayrshire, and are from the shale over- 

 lying the Clay-band Ironstone at Barkip, Dairy. I have 



1 Possibly it is not, as Agassiz never saw the specimen, but drew up 

 his description from a drawing sent to him by Messrs Buckland and De 

 la Beche. As reproduced in the plate in the " Poissons fossiles," this drawing 

 looks like a very hurriedly executed pen-and-ink sketch, from which it is 

 quite impossible to identify anything. Under these circumstances I doubt 

 whether the term " cclmvicensis" has any more value than a mere manuscript 

 name. 



