554 PROP. E. W. CLAYPOLE ON THE STRUCTUEE 



specimens small objects in some respects resembling spines, for 

 which indeed I at first mistook them. But, as above said, no indica- 

 tion of such parts can be anywhere found ; hence this opinion was 

 untenable. An increased number of specimens and closer examina- 

 tion revealed several facts : first, that these apparent spines were 

 margined with what appeared to be a flat fringe around their 

 smaller and pointed ends and nearly to their bases ; secondly, that 

 the rounded conical parts were filled with matrix and had there- 

 fore not originally consisted of hard material ; thirdly, that this 

 central spine-like portion was covered with a layer of the same 

 tissue as that of which the shield was composed ; and fourthly, that 

 the fringe around the conical central portion was distinctly striate 

 in a direction approximately parallel to its axis. The resemblance 

 of this structure to a Crossopterygian fin was now obvious, yet as 

 no such organ had been found with any Pteraspid I was unwilling 

 to attach much value to this resemblance until a single specimen 

 showed the organ so close to the side of the dorsal shield as 

 irresistibly to suggest a connexion. Unfortunately the matrix here 

 obscures the possible contact, and adheres so firmly that separation 

 is impossible without destroying whatever evidence may exist. 

 This, however, is scarcely to be counted an objection to the view 

 above suggested, inasmuch as actual connexion may have been 

 severed before fossilization took place by the decay of the soft parts 

 through which union with the body must have been eifected in 

 order to allow of movement. 



I have represented the three specimens of this singular fossil in 

 fig. 6, wherein are shown the slight differences that exist in size, 

 proportion, and detail. In fig, 7 (p. 555) I have also represented 

 the one specimen showing the organ in the position in which I have 

 written of it above. Four of these ' fins,' if I may venture to so 

 name them, are in my possession, and I 



have seen indications and imperfect traces Fig. 6. — Three ''Jins,^ 

 of others. showing differences 



"Without seeming too positive on this of form and size. 



question, I may further remark that there 

 is no antecedent improbability in this view 

 and no real ground for scepticism. Though 

 we know that the hinder end of Pteraspis 

 was not clad in armour but in scales, so 

 that the caudal and dorsal fins would, if 

 present, fall to pieces on the decay of the 

 soft retaining-parts, yet we have no reason 

 to assume that the same was true of the 

 anterior limbs, hitherto altogether un- 

 known. They might naturally be clad in •^^^©^ 

 the same protective armour as the rest of ■'*=^^^^ 

 the fore body, though movable as the spine 



of Pterichthys. True, it is not usual to find the fins of fishes severed 

 from the body and yet remaining tolerably entire as in the present 

 case, but in creatures so anomalous as these such a state seems 



