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LETTER XIV. 



A/LCYONITES AGREEING IN THEIR FORMS,* BUT DIFFERING IN 

 THEIR STRUCTURE.... SPECIMENS OF FROM FRANCE, ITALY, SWIT- 

 ZERLAND, AND ENGLAND.. ..WILTSHIRE ALCYONITE. 



1 HE fossil alcyonium, which I next present to your notice, is consi- 

 dered as very rare, both by Mons. d'Annone and Mr. Walch. It is 

 figured in Knorr's elegant work, Tome II. Planche, F. 3, from a 

 specimen obtained, as were those in my possession, from Randen- 

 berg. This fossil is figured Plate XL Fig. 2, where it will be seen ap- 

 proaching to a hemispheric form : its lower part, where was its pedi- 

 cle, being somewhat conical, and its superior part, which is somewhat 

 rounded, having a considerable cavity in its centre. The substance of 

 the fossil is divided into numerous lamellae of considerable thickness, 

 perpendicularly disposed round this centre, and concentrated at the 

 conical projection in the inferior part. Between these lamellae are 

 grooves of about a quarter of an inch in depth, which are transversely 

 divided by grooves less deep, and much more irregularly disposed. 



Anxious to obtain some information respecting the structure of this 

 strangely formed mass, I devoted one of the surious specimens which 

 I possessed to suffer the required examination. By means of attri- 

 tion on a sand-stone of considerable hardness, a polished section was 

 obtained on its superior part. On examining this carefully with a 

 lens of considerable power, the substance of the alcyonium appeared 

 to have been formed in this part of minute tubes, opening side by side, 

 in lines crossing each other at right angles. To illustrate this arrange- 



