454 Mr. James Sowerby on a fossil Shell 



elude that these testacea must have been monstrous. We mea- 

 sured one 12 millimetres (*47 of an inch) thick, while the largest 

 kind of pinna known is only '08 of an inch thick/' Conceiving 

 that I knew these fragments from their fibrous structure, I felt 

 satisfied from the active state of inquiry that it would soon be 

 understood, and for some time I paid very little attention to the 

 subject ; but my friends from time to time sending me specimens, 

 none of which gave me the idea of a pinna, I was induced to ima- 

 gine that this common shelly substance varied much in form, and 

 so much so, that the generic names sent with specimens also va- 

 ried, and that it would eventually prove to form a distinct genus. 

 In the opinion that the striated fossil spoken of by Brongniart and 

 Cuvier is the same as those sent to me from various places, I am 

 confirmed by a remark of the Rev. W. Conj^beare, in the second 

 volume of the Transactions of the Geological Society, where I find 

 several specimens figured, and the following observation : " the 

 flat surface of a flint has been originally occupied by a large piece 

 of the striated shell, the fragments of which occur so abundantly 

 in the chalk strata and accompanying the flints, being very com- 

 monly considered as mutilated portions of fossil pinnaz" At page 

 179 of the same work it is mentioned, that there are found in the 

 chalk with flints, "a longitudinal transversely rugose ostrea-form 

 bivalve, of a fibrous structure, and fragments of another fibrous 

 shell of a large size and unknown genus/' The expressive figures 

 annexed to Mr. Conybeare's paper confirm my suspicions as to 

 the identity of these shells, but not that they belong to the Pinna 

 genus ; indeed, from a fragment of a hinge mentioned by Cuvier 

 as in the collection of M. Defrance, I am happy to find that, 

 greatly coincident with my own opinion and observations, some 

 doubt has arisen and suspicion been created that these shells are 

 not Pinnce. 



About twenty-three years since, before my time was so much 



occupied 



