Entirons of Lons le Saitnier. 145 



the regular and constant form of the first, the abundance of 

 various shells, as it were exclusively found in the second, 

 or lastly the existence of very pure crystals of strontian in 

 the midst of the latter, the mass of which does not appear 

 to contain any of the constituent parts of that substance. 



The explanation of these facts is yet a problem, the solu- 

 tion of which would be most interesting. 



Above the very shelly bed, the marls become bituminous, 

 and contain an innumerable quantify of small flat bivalves, 

 of the breadth of a lentil, only distinguishable by their 

 transverse and almost circular striae. 



The action of the air in the first place divided these marls 

 into thin laminae, resembling the finest slate, and afterwards 

 reduces them to powder. 



Besides these microscopic shells, lamins: with impressions 

 of very flat ammonites and planulites (planulites), are met 

 with, as also some small entrochi or baculites. 



Tenaceous beds from 12 to 24 centimetres [about 5 to 10 

 in.] thick, occur in the midst of these bituminous marls, con- 

 taining small veins of black and brown bitumen, divided in a 

 rectangular manner by very fine white spathose partitions;* 

 the rock itself is impregnated by a great quantity of bitu- 

 men ; impressions are there seen of wide planulites (planu- 

 lites), anomiae, a thin and brittle triangular bivalve, and 

 many other genera of shells as difl&cult to determine as the 

 latter. 



I observed a height of more than 20 metres [about 65 ft.] 

 of these bituminous slaty marls, and I have not perceived 

 their upper termination, which proves that they are still more 

 extensive. 



Marls without bitumen succeed them, and rise to the first 

 oolite beds ; they are imperfectly slaty, and in a great mea- 

 sure earthy ; they contain at their upper part beds of shelly 

 and marly limestone, between which are found large ammo- 



* A flattened kind of black fossil wood, which splits into rectangular 

 pieces, separated by thin spathose partitions occurs in the lias marls of 

 Lyme Regis, as also detached flat pieces of a similar nature, the vege- 

 table structure of which is not apparent. (Trans.) 



K 



