556 PEOP. E. W. CLAYPOLE ON THE STEUCTURB 



above is all the evidence that I can offer in support of the opinion 

 herein expressed. 



In opposition to this view may be adduced the structure of 

 Cephdlasj)is, which, so far as we yet know, was possessed of no 

 organ similar to that above described. The appendages to the 

 cephalic plate of which traces are so frequently seen in the fossils, 

 but which has been so rarely preserved in a satisfactory state, h-eve 

 been regarded (as, for example, by Lankester) as pectoral fins, or as 

 doing a double duty (1) as fins and (2) as accessory breathing- 

 organs, resembling in this latter respect the ' gill-scoops ' or scapho- 

 gnathites of the Lobster and the Crayfish. But in these parts of 

 Cephalasjjis, as Lankester says, there is no trace of fin-rays, they 

 being simply elliptical expanses. On the other hand, these organs 

 in Falceaspis do show what may be regarded as rays and what 

 indeed cannot but suggest fin-rays to the eyes of the ichthyologist. 

 In size also they correspond with what might be expected, so that 

 all considerations lead us to the conclusion above stated. But, at 

 the same time, as no specimen has yet shown them indisputably in 

 place, we must suspend our final decision until some happy accident 

 shall, as in the case of Kunth and Von Alth, bring forward absolute 

 and incontrovertible proof either for or against this view. At 

 present the Cephalaspids and the Pteraspids stand alone in the 

 vertebrate sub-kingdom in not possessing or being known to possess 

 paired limbs, unless the low, existing Lancelet {Amphioxus) be set 

 down in the same category. I make no mention of the Serpents, 

 because they are without doubt descended from limbed ancestors, a 

 conclusion which may indeed be true of the Lancelet, but cannot be 

 predicated of the Silurian fishes. 



Though no specimen (as aforesaid) actually shows this organ in 

 position, yet I am induced to believe that it was attached to the 

 body at the critical point already mentioned, where the lateral 

 plate ends forwardly, and where the remarkable change of direction 

 is to be seen in the striation ; a.nd if from this point towards the 

 head the dorsal and ventral plates were not in actual contact there 

 would be here ample opportunity for attachment to the soft parts 

 of the body within, as is the case with the Trunk-fishes or Ostra- 

 cionts of to-day. 



It is fitting here to allude to the fact that Kunth, in his paper 

 already more than once referred to, makes mention of some such 

 organ, and I was at first inclined to hope that a confirmation of my 

 theory of the fin-structure of Palceasjjis might be derived from the 

 remarkable specimen which this palseontologist so clearly but 

 mistakenly described. He writes distinctly of an organ which it 

 seemed to him might be regarded as a means of locomotion or, he 

 adds, of getting food.^ But a short examination of his figure 



^ * Auf derlinken Seite befindet sick zwiichen den beiden Schildern noch ein 

 Scbalstiick von stumpf spindelformiger Gestalt, welches etwas langer ist als 

 die oben erwiihnten Segmente und laugs der Rander der Sebilder gelagert ist. 

 Es mag dasselbe irgend welchen Eewegungs- oder Ernabrungsw-rkzeugen 

 angebort baben ; seine Erklarimg muss gliicklicberen Findern vorbebalten 

 bleiben.' — Zeitschr. d. Deutscb. geol. Gesellseb. vol. xxiv. (1872) p. 5. 



