ROBERTS — DISTRIBUTION OF CEPHALASPIS AXD PTERASPIS. 103 
limestones of Devon are ^vitnesses — called by ns Old Red or Devonian; 
and first appeared upon the stage in true tipper Silurian times ; for 
the Fteraspis Ludensis of the Lower Ludlow shales of Leintwardine 
(county Salop) , is the oldest representative of the family. Its discovery 
in these older rocks, though of great interest, did not in the least 
surprise me ; for a sea-deposit, so clearly marked out as httoral by 
its starfishes and its shrimp-like Crustacea, would be the natural 
home of shore-fishes, which Cephalaspides undoubtedly were. 
Moreover, the shells and faci which the Lower Ludlow rock has 
everywhere in keeping, teU a certain tale of its shallow- water condi- 
tion ; and enable us by studying them to read with greater ease and 
increased interest, the record Ts-ritten by succeeding seas. 
Indeed, if we are to understand the physical aspect of the Old Red 
age, we must make ourselves well acquainted with the foregoing 
Silurian ; for no aid will be of greater value to us, or more beautiful 
as a study, than the slow and gradual transition from the deep-sea 
condition which prevailed over the border-counties I am calling 
attention to, during the accumulation of the marine hmestone of the 
Wenlock series, and the inland lakes of brackish water, terminated, 
probably, by wholl}' freshwater conditions, which have left us the 
fine silty shales of the Upper Old Red as their legacies. 
And thus it comes to pass, that not only for the first stages of its 
new physical career, but also for the birth-place of its life- forms, 
the Upper Silurian age is insolubly hnked with the Old Red Sand- 
stone ; and in every exposure of these older rocks, which contain 
littoral crabs and star-fishes, we may reasonably expect to find the 
ancestr}" of the ancient shore-fishes I am describing. But though they 
thus anticipate the age they are popularly said to belong to, they did 
not — so far as we know — live beyond the close of the Old Red system; 
and beyond doubt their metropoHs is in the grey and red comstones 
of Herefordsliii-e and Worcestershire. 
The position of these beds (see section, page 104), which are 
seen in many places in these border counties to pass through 
a tilestone series into the underlying Silurian, is now clearly 
made out, and only their fossil history waits our reading. And 
this must be learnt by us before the true contemporaneous relations 
of the two very distinct rock-series which we together know as the 
Devonian system can be cleared up ; before we can see what com- 
munication, if any, existed between the shallow waters which laid 
sandy sediment in Herefordshire, and the deeper ocean, which has left 
us hard coral-rock and shells, in Devon, Upon the physical boun- 
daries of these waters, Eichwald has some instructive remarks in a 
short memoir prefacing the fish-fauna of his " Lethcea Rossica," in 
which he points out the marked difference between fishes of the 
shore and fishes of the open sea, and describes some new forms of 
osseous fishes from the Devonian rocks of Russia, not urJike our 
EngHsh Cephalaspids. And now I will mention the results of ray 
own hunting among the Old Red quarries, and I hope, by tjfus 
putting others upon the trail, many good fishes may be taken. For 
more specimens are wanted before even their (precise) position 
