Trof. Hull — On the Structure of Trap-rocks. 153 



LOGICAL Magazine, we have reproduced the above diagram ■woodcuts from Mr. E. 

 Ray Lankester's excellent monograph on " The Fishes of the Old Red Sandstones," 

 Pal. Soc. Hon., vol. xxi., 1868, parti, p. 15. — Edit. Geol. Mag.] 



This opinion has been greatly supported by the late Dr. A. Kiinth 

 (Zeitschrift d. Deutschen Geolg. Gesellsch., 1872, p. 1), who found 

 Pteraspis (or Cyathaspis) in one piece, together with Scaphaspis} 



But I cannot agree with Kiinth, who thinks that Pteraspis belongs 

 to the Crustacea ! nor with Eichwald, who supports the old notion 

 of Kner, that Scaphaspis is the bone of a Cephalopod. 



Pteraspis Kneri occurs in the uppermost Silurian beds of Galizia, 

 associated with Leperditia, BeyricJiia, Tentaculites ornatus and tenuis, 

 Orthonota rotundata, Pterinea retroflexa, etc. It is also very abundant 

 in the Eed Marls and Sandstones covering the Silurian Limestone. 

 These sandstones represent the lowest stratum of the Old Eed Sand- 

 stone, and contain, besides Pt. Kneri, remains of Pterygotus and pieces 

 of ornamented tuberculated shields very much resembling those of 

 Pterichthys and Coccosteus. I am satisfied that there exists in Galizia 

 an unbroken succession of Animal life from the Uppermost Silurian 

 strata to the Lowest Devonian, just as is the case in the West of Eng- 

 land, in Herefordshire. (See Murchison's "Siluria," 1867, p. 243.) 



In perusing the valuable Memoir by Mr, Eay Lankester (in vol. 

 xxi., 1868, and vol. xxiii., 1870, published by the Palgeontographical 

 Society), I was sorry to observe that a former article of mine on the 

 Eussian Cephalaspidians (Ueber Thyestes verrucosus iind CepTialaspis 

 ScJirenhii, in Verhandlungen der Kaiserlichen Mineralogischen 

 Gesellschaft, St. Petersburg, 1866) had been overlooked by him. 

 In that article I established the new genus Tremataspis, which, to 

 some extent, connects by its microscopic structure the genera 

 CepJialaspis and Pteraspis. 



I regret that I have not any separate reprints of that article re- 

 maining, or it would have afforded me much pleasure to forward a 

 copy to the author of " The Pishes of the Old Eed Sandstone," but 

 doubtless the " Verhandlungen," etc., exists in the Library of the 

 Geological Society of London, to which I beg leave to refer Mr. 

 Eay Lankester. 



in. — On the Microscopic Structure of the Limerick Carboni- 

 ferous Trap-rooks (Melaphyres). 

 By Pkofessoe. Edward Hull, M.A., F.R.S. 

 (PLATE VIII.) 

 [Read before the Royal Geological Society of Ireland, 12 March 1873.] 



DE. MACALISTEE, in his able Presidential Address, has furnished 

 the Society with a summary of the work done, principally by 

 German petrologists, with the object of determining the mineral 

 constitution and structure of plutonic, metamorphic, volcanic, and 

 other rocks, by the aid of the microscope. Forbes, Sorby, and Allport 

 amongst ourselves have also represented British petrologists in the 

 same field, but perhaps have not been sufficiently forward in giving 



^ For Mr. Lankester's reply to Dr. Kiinth's paper (extracted from the Academy) 

 see infra, p. 190. 



