on the Organic Composition of Chalk and Chalk Marl, 377 



If now the question be asked whether the forms which occur 

 in such masses in chalk belong to it exclusively, and are hence 

 to be considered characteristic of that formation, I am almost 

 disposed to reply in the affirmative. The analogous forms 

 which occur in sea-sand, tertiary sand, and indeed in all mo- 

 dern formations, are viewed for the most part as different and 

 larger species, although of the same genera ; and it does not 

 appear that any of these forms can be referred with perfect 

 certainty to such as are now living in the sea. 



To the theory of the formation of limestone, the observation 

 is important, that these organic deeply-seated relations are 

 not peculiar to the chalk formation. The tertiary calcareous 

 beds consist, in like manner with the chalk, of multitudes of 

 such Polythalamian animals, which compose in many quarters 

 sandy sea-downs of great extent ; and even in the sandy desert 

 of Libya we can recognize distinct Polythalamia. On the 

 other hand, having succeeded in discovering microscopic 

 Polythalamia in the compact flints of the Jura limestone from 

 Cracow, which are of decidedly different forms from those 

 of the chalk, the calcareous animals being Nodosaria urceo^ 

 lata, n. sp., and Soldania elegans, n. sp., and the siliceous 

 Pyxidicula priscal, with fragments of soft sponges, it becomes 

 apparent that such invisible organic bodies were also present 

 in the formation of the Jura limestone. 



On the Geographical Distribution of Living Polythalamia on 

 the African and Asiatic Coasts of the Mediterranean, and in 

 the Red Sea. 



The materials collected by Dr. Hemprich and myself in the 

 Mediterranean refer to four points on the Libyan coast, and 

 one point on the Syrian coast. In regard to a second point on 

 the latter coast (St. Jean d'Acre), I have acquired a knowledge 

 of some forms from the collection of Dr. Parthey. 



From the Red Sea nine forms were made known to us by 

 d'Orbigny, collected from sand presented to him by Deshayes. 

 But from the collections made by Dr. Hemprich and myself 

 from thirteen points along the whole length of the Red Sea, it 

 appears that very numerous forms exist. Of seven of those 

 points, one occurs on the western (African) coast at Suez, and 

 six on the eastern (Arabian) coast, namely, at Tor, Erraie and 

 el Ard, Moileh, el Wusch and Gumfude ; and of the remain- 

 ing six, five are islands on the Arabian side, namely, Sanafer, 



flints, which is partly calcareous and partly siliceous, the original calcareous- 

 shelled animal forms have exchanged their lime for silex, without under- 

 going any alteration in figure, so that while some are readily dissolved by 

 an acid, others remain insokible j but in the chalk itself all similar forms 

 are immediately dissolved. 



