CEPHALASPIDtE. 3 



described a fossil from the Devonian strata of the Laacher See as Palaoteuthis, referring 

 it to the Sejnada. Professor Huxley has since shown this to be closely related to Agassiz's 

 Ceplialaspis Lloydli. Roenier, in referring to Kner's memoir, expressed the opinion that 

 his Pteraspides were tlie remains of Crustacea. 



Whilst matters stood thus with regard to the last two of Agassiz's species of Cepha- 

 laspis, Sir Philip Egerton described, in the ' Quarterly Journal of the Geological Society,' 

 vol. xiii (1857), several new species by far more closely related to his Cepkalaspis Lyellii, 

 namely, C. Murchisoni, C. Salioeyi, and C. ornatus ; and further formed a new genus, 

 Auchenaspis, for the reception of a very small form, which differed from Cephalaspis 

 Lyellii in having the hinder portion of its shield separated as a distinct " neck-plate." 



The genus Menaspis was briefly described (without any figm-e) by Ewald, of Berlin, 

 in 1848 ; and was stated to have affinities with Cephalaspis. His description, however, 

 by no means warrants this conclusion. The fossil was found in beds of Permian age. 



In Russia (1854), Eichwald described a new genus and species allied to Cephalaspis 

 Lyellii, but differing in having no orbital apertures, as Thyestes verrucosus (see fig. 7, 

 p. 16), which Prof. Pander, in his 'Monographic der fossilen Fische des Silur-Systems' 

 (1856), afterwards re-figured and described as Cephalasjns verrucosus, together with another 

 species from the same locality (Rootsikiille), the latter being termed Cephalaspis Schrenhii. 



Mr. Banks, of Kington, in Herefordshire, now discovered two species of Cephalaspnda, 

 allied to Cephalaspis Lloydii, in the Downton Sandstone, and these were described by 

 Professor Huxley and Mr. Salter, in the 'Quart. Journ. Geol. Soc, 1856,' as species of 

 Kner's genus Pteraspis. At the same time these authors withheld their opinion as to 

 the piscine, molluscan, or crustacean nature of the genus. 



Shortly after this, in 1858, Professor Huxley published a most detailed and careful 

 account of an inquiry into the intimate structure of the fossil shields forming Agassiz's 

 genus Cephalaspis, with a view to ascertain the correctness of Kner's conclusions as to 

 the nature of those species which he had separated as Pteraspis. This most valuable 

 essay is contained in the 'Quart. Journ. Geol. Soc.,' vol. xiv, and I shall have to refer to it 

 very largely hereafter. For the present, it is sufficient to say that Professor Huxley 

 conclusively demonstrated that there was no foundation in facts for the supposed 

 resemblance between Pteraspis and Sejna, or between it and any Crustacean armature. 

 Cephalasjyls Lyellii w^as shown to have a bony structure, from which truly C. Lloydii 

 and Kner's species differed very w'idely, but not in such a manner as to render it 

 probable that they were anything but the shields of closely allied Fishes. Kner's genus 

 Pteraspis was therefore definitely adopted for the three latter species of Agassiz's genus 

 Cejjhalaspis, and for the allied forms more recently discovered. 



Another species of true Cephalaspis was next made known by Dr. Harley (' Quart. 

 Journ. Geol. Soc.,' vol. xv, p. 503, 1859): and Mr. Salter in the 'Ann. Nat. Hist.,' 

 July, 1859, described a Pteraspis occurring in the Upper and Lower Ludlow beds of 

 the Silurian series, which is the oldest indication of a Vertebrate animal on record. 



