386 Say on Shells, <$/-c. 



the latter has been taken for Basalt, and M. Lamarck when 

 describing it, inquires " Est-ce un polypier ?'* Madrepora 

 fascicularis, of Volck. and Parkin, in common with F. striata 

 and F. Gothlandicum, is distinguished by the transverse septa, 

 a character which induced me to refer the species here de- 

 scribed to Favosite; they seem therefore to be congeneric, as 

 analogy indicates a participation in the character of osculated 

 paries. 



Amongst the great variety exhibited by this species, we 

 have to remark more particularly the following, viz. : 



1st. Alveoles perfectly free, that is, destitute of aciculi 

 or lamellae, the septa wanting, and sometimes the osculi ob- 

 solete. 



2d. Alveoles filled almost to the summit with the septa, and 

 resembling those combs of the bee-hive which are filled with 

 honey and covered over. 



3d. Paries beset with very numerous, interrupted, alter- 

 nating, transverse lamellae, which are denticulated at their 

 tips, and project towards the centre with various degrees of 

 prominence and irregularity. 



The first variety corresponds with the generic character, 

 and the third approaches the genus Pontes ,• yet so unequivo- 

 cally identical are they, that I have seen them all united in 

 the same mass, and perforated throughout by the osculi. The 

 identity is further obvious by the perfect gradation which 

 renders them inseparable. 



With respect to the transverse septa, I think their presence 

 may be accounted for by supposing that as the animal elongates 

 its tube in consequence of an increase of growth, or in order 

 to maintain an equal elevation with the adjacent tubes, (ren- 

 dered necessary by the origin of young tubes in the interstices) 

 it gradually vacates the basal portions of its tube, and sustains 

 itself at the different elevations, by successively uniting the 

 parietal lamellae so as to exclude the vacuity. That this is pro- 

 bable, we may infer from a similar procedure on the part 

 of several species of testaceous mollusca. Thus some Lin- 

 naean Serpula become camerated, and a familiar instance pre- 

 sents itself in the Triton tritonis, the animal of which adds sue- 



