144 M. CuARBAUT on the 



which I consider may be referred to the genus anomia, is 

 very rare in the Jura every where but in the maris of the 

 oolite formation. 



Between the beds, numerous nodules of tenacious marl 

 exist, possessing very remarkable peculiarities ; they are 

 solids generally of a cylindrical form, the axis of which, 

 from 8 to 10 millimetres [less than i inch] in diameter, is a 

 small tube of iron pyrites, often decomposed, filled with 

 calcareous spar; they resemble in form columns, ballus- 

 trades, eggs, fruits, S(c. ; some are found more than a metre 

 in height, their position is nearly vertical ; the latter tube is 

 sometimes forked ; two are very often joined together, and 

 the form of the solid is always modified in consequence. 



No fossil shells are seen in these detached bodies, whilst 

 on one side, the tubercular nodules, without central axes, are 

 filled with them ; among the shells are found, venus, planu- 

 lites, ammonites, belemnltes, trochi, turritellae, entrochi, 

 baculites, and rarely pectens. They are so well preserved 

 that they appear as if just taken from the sea; some are 

 covered by a very thin bed of sulphuret of iron, which gives 

 them a very beautiful bronzed appearance. 



Lastly, very large irregularly rounded nodules are met 

 with, of a compact and brittle marl, the interior of which 

 afibrds cracks as much as five centimetres [two inches] wide, 

 lined and often filled by sulphate of strontian, of a white or 

 light sky blue colour.* 



After having observed these nodules, situated on the same 

 marls, we know not which to be most surprised at, whether 



* The sulphate of strontian in voluminous crystalline masses, of a 

 very lengthened plate, but extremely brittle, and of a dirty vrhite, more 

 or less blueisli, appears to belong to the inferior masses of the oolitic 

 limestone, and commonly occurs either in cavities of the limestone, or in 

 those of the large shells, such as ammonites. 



The analysis made by M. Bertier has verified the nature of this sub- 

 stance. I have seen it absolutely in the same position lining the cavities 

 of very large ammonites in the bed of Ergoltz, near Liestal, in the en- 

 virons of Basle, accompanied by belemnites, and a shell that appears to 

 be the Lima antiquata of Sowerby. 



