VOL. XLIV.] PHILOSOPHICAL TRANSACTIONS. 313 



conoid or pileated echini, the common echini galeati, the echini clypeati, and 

 some kinds of the echini ovarii, &c. which, though we are certain that they have 

 been marine shells, yet those particular species are not known in the sea : but 

 then several other species of that same genus are. The case of this is quite 

 different, since not one single species of such a genus has ever been found. 



The excessive size and thickness of numbers of belemnites described by au- 

 thors, viz. of near 2 feet in length, and above 2 inches in diameter in the thick- 

 est part, others of 3 feet long, and others as thick and long as a man's arm ; not 

 to enumerate those only under a foot in length, and of proportionable thick- 

 nesses, concludes echini of a vast size, to have a number of such spines to move. 



The varieties of the belemnites, how can they quadrate to the spines of one 

 genus of echini only ? Solid belemnites, belemnites with a single crust, or like a 

 tube, with a conic cavity only ; that empty, or otherwise filled with a solid mass, 

 or with a regular jointed body, as the alveolus, belemnites ofvarious magnitudes 

 and thicknesses, &c. can all these varieties be imagined to belong to one genus of 

 shells, which we suppose to exist, to maintain a favourite system ? 



The species of echini discovered are numerous ; and the spines of all those 

 agree in having a hollow axis, which runs proportionably from their basis to their 

 apex, quite different from the belemnites : and for their constitution, a foreign 

 naturalist, a member of the Royal Society, Mr. Klein of Dantzic, who has pro- 

 fessedly written on this subject, could only find of 2 kinds, viz. those of a porous 

 constitution, which he observed only to belong to one genus, and those of a 

 solid shattery substance, like a talcy spar not striated; which is the most ge- 

 neral, and is exactly the same constitution as all the fossil spines, or lapides ju- 

 daic! are. 



Further, the lapides judaici have, at some times, been found adhering to their 

 papillae or tubercles, and with fragments of their shells ; whereas no naturalist 

 has ever found fossil either the shells, or the fragments of such a genus of echi- 

 nus ; nor even any remains proportionable to such large spines. In whatever 

 manner the greater part of such shells may have perished (which is unlikely, if 

 we consider their texture and strength), some must have escaped, when the 

 spines are found in such excessive numbers every where, and always perfect and 

 regular ; whereas the fossil spines, or lapides judaici, as they are called, as also 

 the echini or shells, and all the fossil bodies of marine origin, are found broken 

 and shattered in all kinds of manners. 



As for their being shells of the tubuli kind, his reasons against it are : Were 

 the belemnites such, they must be all tubular, more or less ; or otherwise must 

 have suffered some degree of petrifaction to fill up their cavities. The unreason- 

 ableness of that argument is demonstrated by all belemnitas being of one and the 

 same texture and constitution ; though numbers are solid, and numbers are tu- 



VOL. IX. S s 



