1857.] EGERTON — FISH-REMAINS FROM LUDLOW. 285 



the various degrees of compression and consequent expansion to 

 which the buckler has been exposed, no great reliance can be placed 

 upon them ; but, on comparing them with a specimen of Cephalaspis 

 Lyellii, as near as may be in the same condition of preservation, Mr. 

 Lightbody's species very nearly resembled the typical species in the 

 form of the anterior portion of the cephalic disk. The orbits, how- 

 ever, appear to have been relatively larger, more approximated, and 

 more distant from the snout. The most striking feature in this Ce- 

 phalaspis is the form of the hinder margin of the shield. In Cepha- 

 laspis Lyellii this margin advances forward from either side of the 

 occipital crest to a considerable distance, and thence sweeps back- 

 wards to form the lateral armatures of the shield, like two high 

 arches springing from a central pillar. The curvature of this border 

 is so great that it would be indicated by a very small portion of this 

 part of the shield. In the specimen under consideration nearly an 

 inch of the border is preserved on either side the occipital region, 

 apparently in its natural position, without any appreciable signs of 

 accidental fracture or tension. The curvature of these portions is so 

 slight, that, if produced to meet the periphery of the shield, the result 

 would be that, in lieu of the sharp elongated spines so characteristic 

 of Cephalaspis Lyellii, the posterior external angles would be short 

 and blunt, and the general outline of buckler rather semicircular 

 than crescentic. The posterior margin of the shield is strengthened 

 by a thickening of the bone, forming a marginal rib similar to that 

 described by the late Mr. Hugh Miller and myself in the carapace of 

 the genus Pterichthys. The structure of the bones in this species is 

 remarkably coarse and fibrous, and the vascular impressions are large 

 and sinuous. The characters of the dermal integument are not dis- 

 closed in either of the specimens of this species, but the subjacent 

 layer exhibits the carious polyhedral structure common to this genus 

 and the allied Pteraspides. 



One remarkable feature, as seen in the larger of Mr. Lightbody's 

 species and having reference to the generic peculiarities of the Cepha- 

 laspis, remains to be noticed. In all the specimens of the genus 

 I have hitherto examined, the eyes would seem to have been situated 

 in foramina in the bony envelope of the cranial cavity ; but there 

 is evidence here to show that the base of the orbit was closed by a 

 layer of bone, and that the eye-ball was lodged in a comjilete bony 

 socket: PL IX. fig. 1. 



It is much to be desired that some additional evidence may be 

 obtained to complete the specific details of this interesting Cepha- 

 laspid ; in the meantime, as I have little doubt of its specific dis- 

 crepancy from Cephalaspis Lyellii, I should wish to dedicate this 

 new member of the genus to the distinguished author of the ' Silu- 

 rian System,' by the name of Cephalaspis Murchisoni. 



The specimens next to be described are from dark micaceous 

 shales in the cutting of the Hereford Railway at Ludlow. 



Cephalaspis ornatus, spec. nov. PL IX. figs. 2, 3. 

 These reveal another species of Cephalaspid, well characterized 



