94 F. Gluvpman : 



DESORIPTION. 



Family CEPHALASPIDiE. 



Genus T/ivesfes, Eicliwald. 



Thyestes magnificus, sp. nov. 



Specific Characters. — The remains of this fish available for 

 description consist of more than two-thirds of the dorsal surface 

 of the head shield, together with two and part of a third series 

 of Dorso-lateral plates, which are fused to the shield posteriorly. 

 The fossil is preserved in a limonitic raudstone, and apparently 

 the external layer of the shield and posterior plates is partially 

 dissolved away ; l)ut, in spite of this, the surface tuberculations 

 are represented in strong relief. The Cornua are wanting, but 

 there are indications on the matrix that they were incurved and 

 comparatively short. 



Head Shield truncately rounded in front and narrower in that 

 region than is usual in the genus. Sides gently rounded and sloping 

 outwards, having a shallow inflection near the n)iddle of the 

 lateral margins. F^order of head shield formed by a strong rim, 

 rounded dorsally, whilst just within, on the anterior and antero- 

 lateral margins, lies a series of short, parallel, oblique bars 

 (borders of the marginal cells), cut oft' by an inner border, 

 bounded in turn by a series of tubercles. The inner border of the 

 head shield leaves the lateral margins at a distance of about 

 13inm. from the middle of the anterior rim, curving sharply 

 backwards to meet the inter-orliital ridge. 



Surface of Shield (Dorsal), originally more or less convex, but 

 now irr-egular through distortion and slight crushing on the 

 right lateral side; covered with numerous somewhat large 

 tubercles, each seated in a depressed area, usually hexagonal, the 

 sides of which appear to be finely and radiately striate, as in 

 certain figui-ed specimens of Cephalaspis lyelli.^ The hexagonal 

 tesselation of the shield is best seen in our specimen towards the 

 left posterior angle. 



1 cf. Agassiz. Poiss. Foss., vol. ii., pi. 16, tijjs. 1,2. 



