VOL. VIII.] PHILOSOPHICAL TRANSACTIONS. 121 



Of Trochitce and Entrochi* By Mr. Lister. N° 100, p. 6I8I. 



I send you an account of some of the parts of certain stones figured like 

 plants ; which Agricola (5° fossilium) calls trochitae, and the compound ones 

 entrochi ; we in English, St. Cuthert's beads. Agricola thinks them akin, for 

 substance, to the lapides judaici; and indeed these are of an opaque and dark 

 coloured spar ; though some are of a white spar or cawke, as the miners call it : 

 they all break like flint, pollished and shining. Put into vinegar, they bubble, 

 and are dissolved. But this is true of all fossils, whatever their figure may be, 

 that vinegar will corrode and dissolve as a menstruum ; provided they be broken 

 into small grains, and if the bottom of the vessel hinder not, they will be moved 

 from place to place by it. 



The figure of trochitae is cylindrical; the utmost round or circle is in general 

 smooth ; both the flat sides are thick drawn with fine and small rays, from a 

 certain hole in the middle to the circumference. Two, three, or more of 

 these trochitas joined together, make up that other stone, called entrochos. 

 The trochitae or single joints are so set together, that the rays of the one enter 

 into the furrows of the other, as in the sutures of the skull. They are found 

 very plentifully in the scars at Braughton and Stock, small villages in Craven. 



As to their size, I never yet met with any much above two inches about ; 

 others are as small as the smallest pin, and of all magnitudes between these two. 

 They are all broken bodies ; some shorter pieces, some longer, and some of 

 them real trochitae, that is, single joints only. I never found one entire piece 

 much above two inches long, and that very rarely too ; in some of which long 

 pieces, I have reckoned about 30 joints. And as they are all broken fragments, 

 so they are found scattered, and lying confusedly in the rock ; which in some 

 places, where they are to be had, is as hard as marble ; in other places soft and 

 shelly, as they call it, that is, rotten and perished with the wet and air. And 

 though in some places are but sprinkled here and there in the rock, yet 

 there are whole beds of rock of vast extent, which for the most part consist of 

 these, and other figured stones, as of bivalve, serpentine, turbinate, &c. as at 

 Braughton. 



The injuries they have received in their removal from the natural position, 

 if not the place of their growth and formation, are manifest. For, besides their 

 being all broken bodies, many of them are depressed and crushed, resembling 



* The petrified bodies described in this paper belong to different species of the coral tribe, and 

 principally to tliose of tlie Linnaean genus isis. Those at fig. 25 and 26 are the knots or thicker joints 

 «f some radiated isis, and are allied to the species called by Linnaeus isis entrocha. 



VOL. II. R 



