537 



ments of (hells the exuvice of other animals, are as little 

 deferving a place amongft Tcjlacea, as thofe formed 

 wholly of fand, or compofed of both : fuch are equally 

 extraneous fubftances, foreign to the animals, and are 

 only attached by a inuciis, or glutinous fecretion, which 

 forms the internal coating, and is the only part of fuch 

 tubes really belonging to the animals ; and which, in any 

 fpecies cannot be termed more than coriaceous, but 

 more comm.only membranaceous, of a thin, flimfVj 

 flexible fubftance when moift, but extremely fragile 

 when dry. 



It may be afls.edwhy, as we do not confider the Sa- 

 bella in the lead connefted with fhells, nor even deferv- 

 ing a feparate place in the Syflem of Nature, wc have 

 deviated from our hypothecs. To this we fliould reply, 

 that we have only followed the example of greater natu- 

 ralifts, at the fame time fubmitting our obfervations to 

 thofe, who may hereafter take up the fubjeft on a more 

 enlarged fcale. 



We are aware it will be faid, that fliells arc onlv the 

 ■coverings of animals ; granted ; but they are really tef- 

 taceous, wholly fecreted, and prepared by the animals, 

 and as much a part of them, as the coveriiig of a tor- 

 toife, which is infeparably fixed. We admit, however, 

 that it is an imperfeft clafs in the Sxftema Nttip ce, and * 

 was originally rejefted by Linn/EUS as fuch: but as it 

 \vas impoffible to bring thei feveral animals into any 



Z z z regular 



