464 British Association — J. Home, F.R.S., etc. — 



him to give a new classification of the Ostracodermi, and to enlarge the 

 order of the Heterostraci, which now includes four families, instead of the 

 Pteraspidse alone. He has further shown that the Coelolepidae were not 

 Cestraciont sharks to which the Ondms spines belonged, but Heterostraci, 

 though probably of Elasmobranch origin, judging from the shagreen-like 

 scales. The Coelolepidse are common fishes in the Ludlow and 

 Downtonian rocks of Lanarkshire. The genus Thelodus, first described 

 by Agassiz from detached scales in the Ludlow bone-bed, and subsequently 

 figured and described by Pander and Kohon from scales in the Upper 

 Silurian rocks of Oesel, is here represented for the first time by nearly 

 complete forms. But it is remarkable that no Onchtis spines, nor any 

 Pteraspidse, nor Cephalaspidse have been found in the Lanarkshire strata, 

 the nearest related genus to Cephalaspis being Ateleaspis, which, however,, 

 represents a distinct family. 



The group of sandstones, conglomerates, shales, and mudstones that 

 form the passage-beds between the Ludlow rocks and the Lower Old Red 

 Sandstone in Lanarkshire are now regarded as the equivalents of the 

 Downtonian strata in Shropshire, and are linked with the Silurian 

 system. The mudstones of this group, containing the new fish fauna, 

 likewise yield ostracods, phyllocarid crustaceans, and eurypterids — forms 

 which connect these beds with the underlying Ludlow rocks. The band 

 of greywacke-conglomerate, that extends from the Pentland Hills into 

 Ayrshire, composed largely of pebbles derived from the Silurian tableland, 

 is now taken as the base-line of the Lower Old Red Sandstone on the 

 south side of the great midland valley of Scotland. 



The period under review has been marked by important additions to 

 our knowledge of the Old Red Sandstone formation. In 18*78 appeared 

 a valuable monograph by Sir Archibald Geikie on " The Old Red Sand- 

 stone of Western Europe,"^ by far the most important treatise on this 

 subject since the publication of Hugh Miller's classic work in 1841. 

 Following up the view maintained by Fleming, Godwin- Austen, and 

 Ramsay, that the deposits of this formation were laid down in lakes 

 or inland seas, he defined the geographical areas of the various basins in 

 the British area, giving to each a local name. He gave an outline of 

 the development of the rocks north of the Grampians in Caithness, 

 Orkney, and Shetland. He advanced an ingenious argument in favour of 

 correlating the Caithness flagstone series (middle division, Murchison) 

 with the Lower Old Red Sandstone south of the Grampians. He 

 contended that " the admitted palseontological distinctions between 

 the two areas are probably not greater than the striking lithological 

 differences between the strata would account for, or than the contrast 

 between the ichthyic faunas of adjacent but disconnected water basins at 

 the present time." Sir A. Geikie fm-ther gave a table showing the vertical 

 range of the known fossils of the Caithness series from data partly 

 supplied by the late Mr. C. Peach. 



During the last quarter of a century Dr. Traquair has made a special 

 study of the ichthyology of the Old Red Sandstone and Carboniferous 

 strata of Scotland, which has enabled him to throw much light on the 

 distribution of fossil fishes in these rocks and on their value for the 

 purpose of correlation. His researches show that the fish fauna of the 

 formation south of the Grampians resembles that of the Lower Old Red 

 Sandstone of the West of England and adjoining part of Wales in the 

 abundance of specimens of Cephalaspis, the common species in Forfarshire 

 (C. Lyelli, Ag.) being also indistinguishable from that in the Herefordshire 

 beds. Pteraspis occurs in both regions, though of different species. Of 

 Acanthodians Parexus recurvus, Ag., occurs in both, together with 

 ' Trans. Roy. Soc. Edinb., vol. xxviii, p. 345. 



