1857.] EGERTON FISH-REMAINS FROM LUDLOW. 289 



(fig. 7). It is about an inch and three-quarters in length, but is 

 imperfect at the lower end. It is much curved, and the posterior 

 edge is armed. Both these characters separate it from the genus 

 OnchuSy as now restricted*. The longitudinal ribs are fine and 

 numerous, and show a tendency to tuberculation not found in 

 Onchus. Near the base and in the neighbourhood of the posterior 

 margin, the tubercles are distinct. The ribs, although continuous, 

 are constricted at intervals, as in the genus Ctenacanthiis. In many 

 of these particulars this ray corresponds with the genus Byssacan- 

 thus ; but it differs in being compressed rather than cylindrical. It 

 has some resemblance to the posterior part of an Ei^ismacanthus spine. 

 A specimen (fig. 5) from the grit-bed opposite the Paper- Mill, in 

 which Cephalaspis Murchisoni was found, much resembles the above. 

 It is however shorter, more curved, and broader at the base. These 

 characters are such as would attach to the spine of the second 

 dorsal fin, and are not to be relied upon as specific differences, espe- 

 cially since in the more significant features there is a close approxi- 

 mation between the two specimens. 



EXPLANATIONS OF PLATES IX. & X. 



PL IX. fig. 1. Cephalaspis Murchisoni ; inside of cara- "I From opposite the Paper- 

 pace. J Mill, near Ludlow. 

 2. C. ornatus ; outside of carapace. 

 3 a. C. ornatus ; anterior portion of carapace. 



3 b. The same ; portion of the surface-orna 



ment, magnified. 



4 a. Auchenaspis Salteri ; carapace. 

 4 b. The same ; magnified. 

 5. A. Salteri ; another specimen. 



PI. X. fig. 1 a. Cephalaspis Salweyi ; carapace. 

 1 b. The same ; eye-capsule. 



1 c. The same ; portion of the surface-orna- 



ment, magnified. 



2 a. Plectrodus ; portion of jaw. 



2 b. Part of the same, magnified. 



3 a. Plectrodus ; part of a jaw, with the im- 



pression of a larger portion. 

 3 b. The same ; magnified. 



3 c. The same, end-view, magnified. 

 A a. Plectrodus, portion ot jaw. "1 From the Railway-cutting, near 



4 b. Part of the same, magnified. J Ludlow. 



ha. Ichthyodorulite. 1 ^ -a ^i, t> ^^-n 



c I r» ■*- c *.\ -A ^ r. -c^A r- J rom opposite the Paper-M ill. 



5 0. Rugosity of the ridges, magnified, j *'*' f 



6 a. Onchus Murchisoni ? ; fragment. "] 



6 b. Portion of the rugose interior surface, magnified, j 



7a. Ichthyodorulite, [From the Rail- 



7 b. Rugosity of the ridges, magnified. f way-cutting. 

 7 c. Cast of portion of the rugose interior surface, j 



magnified. J 



* Poissons du Vieux Gres Rouge, p. 117. 



From the Railway- 

 >■ cutting, near Lud- 

 low. 



From the Old Red 

 Sandstone at Acton 

 Beauchamp. 



From opposite the 

 Paper-Mill, near 

 Ludlow. 



