26 OLD RED SANDSTONE FISHES. 



Genus 2. — Cyathaspis, Lankester. Brit. Assoc. Rep., Trans. Sect., p. 58, 1864. 



Syn. Ptekaspis (Banksii), Huxley and Salter. Quart. Journ. Geol. Soc, vol. xii, p. 100, 

 1856. 



Derivation. — KvaQoq, a spoon ; aairiq, a shield. 



Characters. — Scutum ceplialicum ovale, aliquanto elongatum, postice truncatum 

 et brevi-spinosum ; in quatuor partes divisum, — rostrum breve anterius, — cornua duo 

 lateralia, marginibus scuti admodum depressis formata, — centralem discum. Superficie 

 striis et liris longitudinalibus, in rostro transversis, ornata. 



General Bemarks. — The ■ evidence on which this genus is formed is more scanty 

 than that on which the foregoing and the following genus rest. At the same time, it 

 appears impossible to associate Vteraspis {Ci/athaspis) Banksii of the Downton Sandstone 

 v^ith either the simple oval-shielded Scaphaspis or the more elaborate Bteraspis. The 

 specimens that I have examined are not very good or satisfactory examples, though they 

 are, I believe, the best yet discovered ; and from them it appears that in these shields 

 the anterior portion is marked off as a distinct rostrum, projecting beyond the rest of 

 the oval scute ; the sides are much depressed, and also marked off from the rest 

 of the scute, the demarcated pieces extending on each side to the rostrum, from which 

 they are similarly separated. This "marking off" is effected by a break in the 

 parallel striations of the upper surface, by a linear groove emarginating each portion, 

 and by dissimilarity in convexity and curvature of the marked-off segments. These 

 pieces had in all probability each a distinct development and growth, as in Bteraspis. 

 The lateral pieces correspond to the lateral cornua of that genus ; the spine and 

 orbital parts are not distinct pieces ; the former being but a spinous tubercle on the disc 

 when it occurs, and the latter in all probability are connected with the rostrum. Some 

 casts of Cyathaspis shields show a marginal tubercle on either side the rostrum, cor- 

 responding with similar tubercles in Bteraspis casts, which are produced by the supposed 

 orbital aperture. I have not had specimens which show the shield itself of Cyathaspis 

 sufficiently well to demonstrate the nature of these tubercles in the casts, but it seems 

 probable that they are connected with the orbits. The species belonging to this genus, 

 concerning which more information would be most welcome, are two in number at 

 present ; one is known by a score or so of poor specimens from the Downton Sandstone 

 of Kington, the other by a single fine internal cast from the Cornstones of Herefordshire. 



1. Cyathaspis Banksii {Huxley and Salter). PI. U, figs. 9, 10, 11 ; and PI. IV, fig. 6. 



Syn. Pteraspis Banksii, Huxley and Salter. Quart. Journ. Geol. Soc, vol. xii, p. 100, 

 pi. ii, fig. 2, 1856. 



Derivation. — Named after its discoverer, Mr. Banks, of Kington. 



