The SKREW-GUT of the RAJA, described by Steno's Son. Sent by Dr. Swammerdam with some other particulars mention'd in the first Section. It winds between parallel lines like a Screw or Stair-case.

But I leave this, and proceed to a remark of my own; and it shall be, if you please, concerning Petrified Shells; I mean such Shells, as I have observed in our English stone-Quarries. But sir, let me premise thus much, that I am confident, that you at least will acquit me, and not believe me one of a litigious nature. This I say in reference to what I have lately read in Steno's Prodromus, that, if my sentiments on this particular are somewhat different from his, it proceeds not from a spirit of contradiction, but from a different view of Nature. First then, we will easily believe, that in some Countries, and particularly along the shores of the Mediterranean Sea, there may all manner of Sea shells be found promiscuously included in Rocks or Earth, and at good distances too from the Sea. But, for our English-inland Quarries, which also abound with infinite number and great varieties of shells, I am apt to think, there is no such matter, as Petrifying of Shells in the business (or, as Steno explains himself p. 84. in the English Version, & alibi, that the substance of those shells, formerly belonging to animals, hath been dissolved or wasted by the penetrating force of juices, and that a stony substance is come in the place thereof,) but that these Cockle-like stones ever were, as they are at present, Lapides sui generis, and never any part of an Animal. That they are so at present, is in effect confessed by Steno in the above cited page; and it is most certain, (2283) that our English Quarry-shells (to continue that abusive name) have no parts of a different Texture from the rock or quarry they are taken, that is, that there is no such thing as shell in these resemblances of shells, but that Iron-stone Cockles are all Iron stone; Lime or marble all Lime-stone and Marble; Sparre or Chrystalline-shells all Sparre, &c. and that they never were any part of an Animal. My reason is: That Quarries of different stone yeild us quite different sorts or species of shells, not only one from another (as those Cockle-stone; of the Iron-stone Quarries of Adderton in York-shire differ from those found in the Lead-mines of the neighbouring mountains, and both these from that Cockle-Quarrie of Wansford-bridge in Northampton-Shire, and all three from those to be found in the Quarries about Gunthrop and Beavour-Castle, &c;) but, I dare boldly say, from any thing in nature besides, that either the land, salt, or fresh water doth yeild us. 'Tis true, that I have picked out of that one Quarry of Wansford very resemblances of Murices, Telinæ, Turbines, Cochleæ, &c. and yet I am not convinced, when I particularly examined some of our English shores for shells, also the fresh waters and the fields, that I did ever meet with (N.B.) any one of those species of shells any where else, but in their respective Quarries, whence I conclude them Lapides sui generis, and that they were not cast in any Animal-mold, whose species or race is yet to be found in being at this day.