Prof. W. King on Spirifer ciispidatus. 9 



specimens, and supposed to be the remains of perforations. 

 This and other considerations prevent me from admitting that 

 Mr. Davidson's specimen was always imperforate — that is, 

 that it absolutely possesses or possessed this negative character. 



It will have been seen that, with the exception of the last 

 three specimens, all the rest show perforations more or less 

 plainly, but associated with others which exist in a very ob- 

 scure condition — so much so that, were it not for their occur- 

 ring in the required place, and being slightly different in 

 translucency, they might be objected to as representing any- 

 thing of the kind : between the latter and the former, however, 

 there indisputably occur all the intergraduating forms. More- 

 over perforations often unexpectedly appear in the midst of 

 wide imperforate spaces — a fact admitted both by Mr. Meek 

 and Dr. Carpenter. 



Now, as the perforations of Spirifer cuspidatus occur in all 

 states of appearance, from the extreme obscure to the perfectly 

 obvious, is it not reasonable to suppose that they may also 

 occur under such conditions as to be imperceptible, and thus give 

 rise to seemingly " imperforate spaces?" Why the perfora- 

 tions are partially absent in some specimens, also totally ab- 

 sent in others — I do not feel myself competent to go beyond 

 suggesting that the cause may be in some way or other con- 

 nected with the metamorphism or mineralization of the test. 

 But Dr. Carpenter declares himself to be strongly in favour of 

 a different view. He " feels certain " that the absence of the 

 perforations " is not the result of any alteration produced by 

 fossilization, the shell-structure being equally well preserved 

 in the perforated and in the imperforate parts"*. The state- 

 ment may be taken for a fact ; but I totally dissent from the 

 conclusion di'awn from it. A few observations on this point 

 may now be brought forward. 



The fact mentioned by Dr. Carpenter is certainly a remark- 

 able one. It, however, not only holds good in the "perfo- 

 rated" and "imperforate parts," but equally so in those which 

 show the perforations very obscurely. The present condition 

 of such perforations is indisputably " the result of alteration ;" 

 yet how does it happen that their associated fibres are " equally 

 well preserved" as in the other cases? Because, from certain 

 incidental causes and structural peculiarities, to be shortly 

 noticed, " fossilization " has had the effect of [nearly in many 

 cases and entirely in others) obliterating the perforations, with- 

 out producing any such results in the " shell-structure." The 

 existence of the cases just referred to is not to be taken simply 



* Ann. & Mag. Nat. Hist. July 1867, p. 71. 



