596 DB RAMSAY H. TRAQUAIR ON THELODUS PAGEL 



portion of body short, narrow, triangular, scarcely half the width of anterior portion, 

 rapidly narrowing to tail, which is long and linear; fins membranous, covered with very 

 small scales in parallel rows ; no demarcation between body and commencement of 

 pectorals ; caudal fin large, entirely below ; scales small, somewhat elliptical in form, 

 umbonate, smooth, inner surface having an elliptical indentation in centre. Branchiae, 

 consisting of exposed arches, arranged seven or eight on each side of, and at right angles 

 to, a ridge running longitudinally along the centre of the under side of the disk, and 

 occupying about one-half its length. Length about fourteen inches." 



Kegarding its affinities, Mr Powrie thus expressed himself : — 



" The peculiar form of the anterior portion of the body and pectoral fin, the lono- 

 linear tail, and, if I am correct in considering the peculiar markings on the under side of 

 the head as the branchial apparatus, it would appear decidedly placoid, and strangely 

 allied to modern Rays ; but at the same time the scales, although small, and somewhat 

 like those of the Acanthodian fishes, are more ganoid in character than those of the 

 latter family." 



In the second part of Mr A. Smith Woodward's Catalogue of the Fossil Fishes in the 

 British Museum, published in 1895, p. 200, the fish is simply mentioned as "Another 

 supposed ally of the Cephalaspidae," there being no remains of it in the London 

 collection. 



In 1894 I myself made a brief allusion to the so-called Cephalopterus, in treating of 

 the remarkable plates from the Old Red Sandstone, known as Psammosteus, which arc 

 now usually considered to have belonged to some sort of " armoured Sharks." Speaking 

 of the external sculpture of these Psammosteus plates, I remarked : — 



" The minute stellate tubercles which form the ornament of the outer layer are clearly 

 shagreen-bodies, which have coalesced, as very similarly shaped bodies, still disunited, 

 may be seen to form the dermal covering in Powrie's Cephalopterus Pagei from 

 the Lower Old Red of Forfarshire, the subjacent thickness of the plate being 

 formed in a deeper layer of the skin." And as the name Cephalopterus had been pre- 

 occupied as early as 1809, I proposed, in a footnote, to re-name the genus Turinia, from 

 the locality whence the specimen was derived.* 



It was not, however, till I became acquainted with a remarkable series of Upper 

 Silurian fishes discovered in Lanarkshire by the Geological Survey of Scotland, and 

 which, having been placed in my hands for description by Sir Archibald Geikik, will 

 form the subject of a subsequent paper, that I discovered the special importance of this 

 hitherto problematic fish from the Forfarshire Old Red, as well as the fact that the 

 name Turinia, which I had given to it, must share the same fate as Cephalopterus, 

 though for a different reason. 



From their squamation, it became clear that some of these Silurian fishes were 

 referable to Thelodus of Agassiz, a genus previously known only by detached scales 



* "The Extinct Vertebrate Animals of the Moray Firth Area," published in Harvie Brown and Bui 

 " Vertebrate Fauna of ike Moray Basin" vol. ii., Edinburgh, 189G, p. 2C2. 



