M. Desnoyers 07i the Chalk of the Cotentin. 255 



croscopical Cephalopodes, which I have never seen in the marls 

 of the chalk, where they are replaced by small forammous 

 corals, Crania and Thecidex. These latter deposits much 

 resemble, as to fossils and incoherence, the beds, also subor- 

 dinate to chalk, of Mirambeau, in the Charente Inferieure, and 

 that of Maestricht. 



The different kinds ofbaculite limestone, such as have been 

 above enumerated, present either, as at Orglandes, uncon- 

 nected and unstratified masses of compact hmestone m the 

 midst of calcareous gravels containing the same tossils, and 

 subordinate to the same formation ; or, as at Bonne Ville, very 

 extended thin beds, uniform tables, for the length ot many 

 yards; or, as at Nehou, isolated marls without solid beds; or 

 lastly, as at Freville, the entire system, composed of many 

 nearly horizontal strata, alternately coherent and friable, com- 

 pact and marly ; incontestably proving the relations of the 

 beds, elsewhere found isolated. The whole, however, as tar 

 as can be judged from the few known places where workings 

 are carried on, of infinitely less thickness than the chalk of 

 the great basins of France and England. 



I am only able to afford a very imperfect idea as to their 

 topographical extent, and shall add nothing to the notices 

 collected by M. de Gerville, who can best assign them their 

 true limits. This rock, more particularly developed to the 

 S of Valofrnes, in a space comprised between Sainte Mere 

 EMise, Montebourg, and Pont I'Abbe, would appear to have 

 a direction from E. to W., and to form one system, at pre- 

 sent interrupted by several small rivers. I have only studied 

 it in the communes of Freville, Cauquigny, Bonne Vi le, Or- 

 glandes, and Golleville, to which list M. de Gerville adds 

 Gourbeville, HauteviUe, Nehou, Rauville, and Sainte Co- 

 lombe. I cannot however assert that all these localities would 

 afford the true compact limestone, equivalent to chalk. 



I have no where very evidently seen the immediate super- 

 position of this rock on those more ancient, though many cir- 

 cumstances connected with relative position and dip lead me 

 to conclude that it rests on the oolite limestone, named Cal- 

 caire de Valognes, at Orglandes and Picauville; on Calcaire 

 avcc Gnjphees arquces* at Cauquigny and Freville, and on 

 transition rocks near Nehou ; but I have no where observed 

 the slightest fact which might lead us to doubt the posteriority 

 of thi^ formati(jn to all of them. I can with certainty affirm 



• Lias : 1 conceived the Freville baciilite limestone as resting upon this 

 rock in the Gcol.'IVans. new scries, vol. i. p. B8. \^-Z2.— Trans. 



that 



