FOSSIL INVERTEBRATED ANIMALS. 497 



liumt and stirps, employed by Pallas and Linnaeus, the first 

 for the stony polyparia, or lithophytes ; the second, for the 

 flexible or corneous polyparia, or ceratophites. 



M. Lamarck thus defines a potypanitwi — a fixed envelope, 

 more or less solid, calcareous, or corneous, in which a poly- 

 pus inhabits, and which is the evident result of a transudation 

 from its body of an excretion through certain pores of its 

 skin of substances sufficiently compounded to form by their 

 approximation a concrete body, more or less solid, and alto- 

 gether inorganic. This definition, in reality, is only applicable 

 to the madrepores of Linnaeus, and also to his escharae. It is 

 scarcely so to the sertulariae, cellariae, and not at all to the 

 isis, coral, and gorgon. Accordingly we find M. Lamarck 

 himself obliged to return to the use of the words stirps, axis, 

 rachis, sterna iSfc, to signify the body, at once fleshy and solid, 

 which forms the common part of the pennatulse, although there 

 are the greatest affinities between this body and that which con- 

 stitutes the solid part of the isis, gorgons, and coral. If we 

 persist, then, in the generalization of the word polyparium, it 

 should be defined as a solid body, calcareous or corneous, the 

 result of one or many polypi, without troubfing ourselves with 

 the mode of its formation or the manner in which the polypi 

 are placed in it. In this sense, the fibrous mass of a true 

 alcyone, the fleshy mass of a pennatula, the corneo-calcareous 

 plate of an eschara, the tubes of the tubulariae, the phytoid 

 stems of the cellarise and sertulariae, the calcareous, arbores- 

 cent, frondescent, and phytoid masses of the madrepores, will 

 all be equally polyparia. We may even range under this name 

 the handsome tufts of corallines, if we admit that they carry 

 polypi, which, however, is not the case. 



In contemplating the nature of polyparia, we find them of 

 many kinds, according as they are calcareous or stony, cor- 

 neous, fibrous, corticiferous, or pasty. 



The first one, called lithophytes, a denomination very an- 

 ciently employed, and which is derived from the idea that 



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