ralised state, lead to the supposition, that the paucity of fossil star-fish 

 depends, either on some circumstance in the original composition of the 

 animal, which renders it little fit to undergo the petrifying change ; or 

 on some circumstance, in its mineral state, which prevents its preserva- 

 tion in its matrix, or its safe extrication from it. All these circumstances 

 have, perhaps, some share in occasioning the scarcity of these fossils : 

 it appears, however, to be chiefly attributable to the original conforma- 

 tion of the covering of the animal, which is the only part which can be 

 preserved to us by mineralization. 



The coriaceous, and even pulpy consistence, of the coverings of these 

 animals, in a living state, plainly evinces, that the mucilaginous or 

 membranous matter, bears a very large proportion to the carbonate 

 of lime, .whicfc -enters into the composition of these bodies. On the 

 cessation 'of fife, * therefore, a speedy decomposition of this animal mat- 

 " ' -' 



ter "mil- ensue v -aa'A. -fF'om a deficiency of earthy matter to support 

 its form, the whole substance must, in general, be resolved into a shape- 

 less mass. 



The crustaceous covering of one of these animals, of a smallish size, 

 was found to be pierced with fifteen hundred and twenty apertures, 

 through which passed, or to which were attached, as many horny tubes; 

 serving, according to M. Reaumur*, either as feet, or as organs through 

 which the water received by the stomach of the animal was ejected. 

 The anatomy of this animal, however, has not, at least to my know- 

 ledge, been pursued so far, as to determine the real use of these tubes, 

 which seem rather to be analagous with the absorbent tubes of the 

 echinus. For our present purpose, it is only necessary to remark, that 

 the membranous matter connecting these tubes with the external crust, 

 or lining the apertures through which these tubes pass, must consider- 

 ably add to the quantity of animal membrane, on the predominance 

 of which its perishable nature so much depends. 



* Obscwatio de Stellis marinis, Sect. VIIL 



