150 Scientific Intelligence. 



fossils being found in all, viz. '* Ammonites placenta, Scaphites Conradi, 

 Baculites oVatus, Nautilus DeKayi, <fcc ." This identification is first an- 

 nounced by Messrs. Meek and Hayden. It is also shown that Inocera- 

 mus problematicus, found in Nebraska, is obtained also in Kansas, aho in 

 lat. 39°, Ion. 98'', and farther towards the Rocky Mts. by Col Fremont, 

 and a shell considered the same, by Roenier in Texas: and that Ostrea 

 congesta, so distinct in Nebraska, was found by Marcou ahd Galisteo be- 

 tween Fort Smith and Santa Fe. The cretaceous formation has a great 

 extension at the west and south. The paper speaks for itself 



C, DEWEV. 



6, Proportion of Bivalves of different Geological Age^, — H. G, Bronn 

 ives the following table in an article on this subject in Leonh, u. Bronn s 

 ahrbuchj 1856, p, 656. — 



y Lamellibranchiatps Lamellibrancbiateg 



Total Tiunrmer Brachiopods. with entire pnllinm. with sinus in palUura. 



of species. Species. Proportion. Species. ProporVn. Species. Fropor. 



Living, 2670 60—0-02 . 1480=0-55 1130=0-43 



Csenozoic, 2497 52=0'02 1555=0-62 890=0'36 



Mesozoic, 3447 371=0-11 2358=0-68 718=0-21 



Palseozoic, 2021 1109=0-50 799=0*40 113=0-10 



The column "proportion" gives the ratio to the total number of species. 

 The c^nozoic includes the Tertiary and Post-tertiaiy ; the mesozoic, the 

 formations below down to the Permian, and the Palaeozoic the remaining 

 below this limit. 



The integripallial bivalves were most numerous in the mesozoic. Di- 

 viding them into the Pleuroconchas (having unequal valves) and Ortho- 

 conchse (equal valves), there are according to Bronn's Lethaea Geognostica, 



Total. Pieuroconchse. OrthoconchEC- 



Living, 1480 330=0-23 1180=0-77 



Csenozoic, 1655 575=0*27 980=0*63 



Mesozoic, 2358 1181=0-50 1177=0-50 



Palajozoic, 799 299=0'87 500=063 



There is no doubt that the Brachiopods are inferior to the other Bivalves, 

 and also that the Integripallials are inferior to the Sinupallials. 



^. Slaty Cleavage. — The view of Mr. Sharpe, presented to the Geo- 

 logical Society of London in 1847, that slaty cleavage is owing simply to 

 pressure and is at right angles to the line of force, has been established by 

 various facts brought forward by Mr. J", Tyndall. (Phil. Mag. [4], xit, 

 35). He shows that a fine clay or almost any impalpable material wheti 

 subjected to pressure and at the same time allowed to spread laterally, 

 takes a laminated structure. White lead, wax, and even cheese are 

 among the substances which have afforded him evidence on this point. 

 He attributes the effect to the small inequalities which exist in the tex- 

 ture of sul^tances of all kinds. Under pressure the mass yields and 

 spreads out, and the little nodules become converted into laminae separa- 

 ted from each other by surfaces of weak cohesion, and thus the mass be- 

 comes cleavable- The air cavities or fissures also spread out thin under the 

 pressure and aid in producing the cleavage : for even dried pipe-clay 

 shows such cavities in great numbers, many too small to be seen without 

 a magnifier. 



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