44 



OLD RED SANDSTONE FISHES. 



Characters. — I must refer to the figures of the two specimens which are considered 

 as belonging to this species for a notion of its characters. It was associated by Agassiz 

 with the heads from the EngUsh Cornstones, which will here be spoken of as Euceplia- 

 laspis Agassizii, since they appear to differ in this point of structure, viz. that the orbits 

 in the Scotch specimens are placed more posteriorly in the shield, and the cornua are 

 less produced and less divergent than in the English heads. At the same time it must 

 be confessed that there is very close agreement in the outline of the head-shield as exhi- 

 bited in the best-preserved specimens. Neither of the Scotch specimens show the surface 

 ornament, so that we cannot compare them in this regard. C. Lyellii and C. Agassizii 

 were undoubtedly very closely allied, but the evidence does not justify their association 

 under one specific name. The figures in the plates give all that is known on the matter. 



General Bemarks. — ^The specimen drawn by Mr. Dinkel in PI. VIII, fig. 1, is the 

 same which he figured more than thirty years ago for Prof. Agassiz. It has since then 

 been worked out a little from the matrix, so as to exhibit the marginal series of scales. 

 In the process the indications of the remarkable pectoral appendages drawn by Mr. 

 Dinkel in Agassiz's plate, but not referred to in the letter-press, have been destroyed. 

 Mr. Dinkel has, however, reintroduced them here, especially on the left side. A false notion 

 of the structure of the body of Cephalaspis has been conveyed by the former drawings 

 of this specimen and the copies in woodcuts illustrating popular treatises on geology. 

 A jointed structure, as though the body were composed of a series of hard rings fitting 

 into one another, has been in this way erroneously attributed to the fish (which mistake 

 was by no means due to Prof. Agassiz, who knew and described the scales). The fact 

 is that the scales of the body are of considerable thickness, and in the celebrated British 

 Museum specimen drawn in PI. VIII, fig. 1, their upper layers are entirely broken away, 

 and only a flake of calcareous matter is left covering in their impressions, and thus pro- 

 ducing the false jointed appearance. The deficiency in the specimen towards the caudal 

 extremity marks the position whence the dorsal fin has been broken away. The other 

 specimen, drawn in PI. XI, fig. 1, which is referred to this species, is with, perhaps, the 

 exception of Mr. Powrie's specimen drawn in PI. X, fig. 1, and referred to C. Poicriei, 

 the most instructive and beautifully preserved remnant of these curious little old 

 Sturgeons which has been found. It belongs to the Museum at Arbroath. The pectoral 

 fins are well shown in the specimen, though I have to explain that my over-zealous friend 

 Mr. Dinkel has given an appearance of a joint to the right-hand pectoral, which is not 

 clearly seen in the fossil itself. The dorsal fin is also well shown, as is the caudal, but 

 it is not so perfectly preserved in this as in another specimen (of another species probably) 

 drawn on the same plate. The woodcut restoration (fig. 16) may help to elucidate 

 the drawing of the fossil. The scales in this Arbroath specimen are unfortunately in the 

 same broken condition as in the Glammis (Brit. Mus.) specimen, and no trace of the sur- 

 face ornament is to be detected. 



The Arbroath specimen has very fortunately been broken in such a way that a piece 



