CEPHALASPID/E. 



61 



Kallostrakon podiira, on account of the resemblance of their ornament to the well-known 

 microscopic markings of the scales of the insect Podiira. The microscopic structure of a 

 portion of the scale drawn in tig. 21, PI. XIII, is given in fig. G, PI. XIV, and is well 

 worth attention, on account of its very peculiar nature. 



The numerous indeterminable fragments of fish remains, together with the Onchm 

 species, which occur in Siluro-Devonian beds require careful collation and study ; they 

 appear to indicate the presence of other (jrotipfi of fish in company with the Cephalaspidte 

 described in these pages. 



B. Since the plates of this Monograph were completed, and the first part issued, 

 a great discovery has been made, or rather a rediscovery relating to its subject-matter. 

 CephalaspidcE have been found in Devonshire and Cornwall, in beds assigned to the Lower 

 Devonian series. Mr. Peach long since (in 1847) described the remains in question as fish, 

 and latterly, from specimens belonging to Mr, Pengelly, the Cephalaspidian nature of 

 the remains, which had in the interun been considered as Sponges, has been decided by 

 the Rev. W. S. Symonds, by Prof. Huxley, Mr. Salter, and myself. Innumerable remains 

 of the shields of a Scapha^sjns, more than a foot long, fragments of Cephalaspis, numerous 

 spines, and other indeterminable fragments, besides the splendid scale and spine 

 assigned by Mr. Pengelly respectively to FJii/lIolepis and Ctenacanthus, are the fish 

 remains of these beds. Mr. Pengelly, i\lr. Peach, and the Royal Geological Society of 

 Cornwall, have kindly lent me their specimens for further examination. 



C. Before leaving the subject, and now that the various forms and remains of the 

 Cephalaspidian Fishes known have been described and figured to the reader, 1 should wish 

 to revert to the question of their zoological position discussed in the first pages of this 

 Monograph. Since they are the earliest remains of Fish presented to us by the geological 

 record, we should naturally expect them to exhibit a diff'erence of organization as com- 

 pared with living fishes, leading us downwards to some invertebrate group. But it 

 cannot be too strongly asserted that these Fishes are, as far as can be seen, by no means of 

 a low type, and that, so far from showing any real affinities with lower types of animal 

 life, such as the fancied relationship with Crustacea or Cephalopoda, they disclose, upon 

 careful examination, points of structure, such as the double olfactory cavities and the pec- 

 toral appendages, which place them very far above some living Vertebrata (Lampreys) 

 classed as Fishes. At the same time there is nothing in the remains known to us which 

 will indicate even approximately their affinities to any one of the large groups recognised 

 in the classification of Amphirhine Fishes. So great is the variation in the distribution of 

 calcareous matter in the exo- and endo-skeletons of Fishes that in these, as in so many other 

 fossil mend)ers of the class, no evidence is given by which we can judge of the condition of 

 the important respiratory, circulatory, and digestive organs which accompanied the skeleton. 

 The calcified skeleton in Cephalaspidce, apparently, was entirely confined to the aponeu- 

 rotic or ' sphnt-system' of Mr. Parker; and whilst the cndo-skeleton was cartilaginous, it 

 may have been of high or low development. Apparently, too, like the Lophobranchs and 



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