Imperfections of Bronigniart s Fossil Tables. 341 



and that, on applying these to the various basins, the exceptions 

 to the rule are nearly as numerous as are the cases in which it 

 proves true. The upper part of the protelque formation does 

 not, as M. Brongniart contends (page 15^), contain a great 

 mass of rolled pebbles and sandstone, that mass occurring in its 

 median part. M. Brongniart also forgets the sands, and we see 

 that he is describing only the Paris and London basins, when 

 he indicates flint pebbles ; besides, the Paris marine Umestone, 

 with its plastic clay and marl, contains also conglomerate and 

 sandstones. 



The shells of the tritonien limestone, in the upper tertiary soil, 

 would be a good character, if they were not, like bones, of rare 

 occurrence. If the fossils enumerated by M. Brongniart, as 

 characteristic of the upper tertiary deposits, did not exist in the 

 tritonien group, we would again have a good geological horizon, 

 because these shells are very abundant everywhere, at least in 

 particular beds ; but unfortunately this is not the case, and then 

 their greater and less abundance in one deposit than another is 

 of no use. In that case are " les cerithes cordonnes les Cytheres, 

 le pectunculus pulvinatus et quelques autres petites huitres," 

 (p. 152). The indications in the inferior parts of the upper 

 tertiary soil, " de beaucoup de pailettes de mica, de lits de 

 marne argileuse et calcaire k grand huitres, d'os de cetacees, now 

 tamment de lamantin, de clypeastres et de peu d'autres echinides,'' 

 are useful but subordinate characters. Besides, if molasse and 

 subappenine clay are micaceous, mica occurs also in sands which 

 are superior to these rocks. Bones are of great value to the cabinet 

 geologist, but of comparatively little importance to the geologist 

 studying the science in the field ; and the more so, as M. Brong- 

 niart is careful not to assert that lamantin's bones do not also 

 occur in other deposits. This may be said of the clypeasters. If 

 great beds of oysters are important, why not also mention great 

 beds of pecten or balanus, &c. ? The species alone can establish 

 some zoological differences amongst the upper and under ter- 

 tiary deposits, as M. Brongniart thus confesses : " Au moyen 

 de hstes aussi complettes qu'il sera possible de les faire, on 

 pourra arriver k obtenir du caracteres tires de rapports nume- 

 riques au defaut de caracteres absolus,"" (p. 369). 



If that desijderatum can be filled up, it will be with very grej|t 



