857.] EGERTON FISH-REMAINS FROM LUDLOW. 283 



ties, so far as I am aware, not one single specimen has been brought 

 to Kght which would have enabled even that distinguished naturalist 

 to pronounce a positive opinion as to its place in the scale of nature. 



The genus Cephalaspis is typified by the Scotch species named, 

 after Sir Charles Lyell, Cephalaspis Lyellii. This species, as recog- 

 nized by the cephalic buckler, is of frequent occurrence in the 

 English beds ; and is associated with other forms, not found in the 

 Scotch beds, differing considerably in general character, but agreeing 

 to a certain extent in structural details. Professor Agassiz refers these 

 to the same genus with hesitation and reservation, for, having described 

 them as Cephalaspis Lewisii and C. Lloydii, he says*, *' It appears to 

 me probable that some day, when better known, these two species 

 should be separated generically from Cephalaspis Lyellii.^' Following 

 out this suggestion. Dr. R. Kner has proposed for these and some 

 allied forms the generic title Pteraspis, a name which has been ac- 

 cepted and adopted by Professor Huxley and Mr. Salter, in describing 

 some new species discovered by Mr. Banks in the neighbourhood of 

 Kingtonf. 



The materials submitted to me for examination are scanty, and 

 afford little scope for detailed descriptions ; at the same time they 

 exhibit new characters of sufficient importance to merit notice. 



Cephalaspis Salweyi, spec. nov. PI. X. fig. 1. 



I will first speak of the specimen found by Mr. Salwey, of Acton 

 Beauchamp. It exhibits the central and greater portion of a cephalic 

 buckler of a large species of Cephalaspis. The peripheral parts 

 are wanting, as are also the posterior angles of the buckler, leaving 

 it doubtful whether or not the latter were extended to form the sharp 

 spurs so remarkable in Cephalaspis Lyellii. The length of the 

 shield from the snout to the posterior angle of the occipital crest is 

 3 J inches ; the breadth from the median line between the orbits to 

 the margin of the shield ly^y inch, which gives 2^^, inches for the 

 entire breadth. The space between the orbits is -^ an inch, and the 

 transverse diameter of the orbit j^q of an inch. From the snout to a 

 point on the median line between the orbits is 1 j^^ inch, and from 

 the same point to the termination of the occipital crest is 2 inches. 

 On comparing these measurements with the corresponding dimen- 

 sions of a specimen of Cephalaspis Lyellii of the same comparative 

 size, it will be seen that the buckler of this species is more elongated, 

 the orbits more distant from each other, and their position more ad- 

 vanced. It may be said, and perhaps with justice, that Mr. Sal- 

 wey' s specimen, from its imperfect condition, does not afford a fair 

 standard of comparison, and that it may only be a portion of a large 

 individual of the known species. I have already stated that the 

 peripheral parts are wanting, and therefore I do not insist on the 

 measurements in which they are implicated. There is, however, a 

 constant character on which to rely in the size and relative position 



' * Poissons Fossiles, ii. p. 152. 



t Quart. Journ. Geol. Soc. vol. xii. p. 93. 



