Page:VCH Cornwall 1.djvu/96

 A HISTORY OF CORNWALL was subsequently recognized by Mr. C. W. Peach, 1 who collected many specimens ; and still later they were assigned by Mr. J. W. Salter 2 to the typical genus Pteraspis, although this determination was not accepted by Professor E. Ray Lankester, 3 who renamed them Scapbaspis cornubica. Even this determination was not, however, final, for in 1898 Dr. A. Smith Woodward, in describing* some of the finely ribbed plates of these fish-like creatures from Lanivet Bay, wrote as follows : ' They have sometimes received the name of Scapbaspis, which now proves to be applicable to the ventral shield of any member of the family ; more recently they have been provisionally assigned to the genus Pteraspis. All the known specimens are, however, very fragmentary ; and hitherto there have been no means of determining their generic relationships. A specimen recently submitted to me by Mr J. H. Collins, and two other specimens in the British Museum, now seem to furnish the neces- sary facts for this determination, and indicate that, so far as the dorsal armour is concerned, the Cornish species truly belongs to the type genus Pteraspis ' It is thus evident that the Cornish Devonian pteraspidian has a complex 6 dorsal shield, that the orbit is completely surrounded by a special orbital plate, and that a short dorsal spine is fixed in a cleft at the hinder border of the median disc. These, in combination, are the special characteristics of Pteraspis as now defined, and prove, as already mentioned, that the Cornish species is correctly described under the name of P. cornubica. It seems to be the largest species of the genus hitherto discovered 'It may be added that in Western Europe Pteraspis is characteristic only of the Lower Devonian or Lower Old Red Sandstone, not descending below the base of this formation, where it is preceded by [forms with] a simple shield, Cyatbaspis. In Galicia, however, typical species occur in strata which are claimed to be of Downtonian or even Ludlow age.' Fragmentary remains probably of Cepbalaspis have also been found with these Pteraspidians 6 ; and some associated plates may belong to the Arthrodiran Phlyctaenaspis.' 1 1 Rep. Brit. Assoc. for 1843, Trans. Sect. p. 56. 2 Geol. Mag. v, 247 (1868). 8 Ibid. 248. Trans. Roy. Geol. Soc. Cornwall, xii, pt. 4 (1899). 5 Misprinted ' complete ' in the original, 6 A. Smith Woodward, Tram. Roy. Geol. Soc. Cornwall, xii, pt. vi (1901). 7 A. Smith Woodward, Geol. Mag. [4] vii, p. 148 (1900).