o?i the Organic Composition of Chalk and Chalk Marl. 451 



cell. In the Nautilus, this projection of the tube of connexion 

 is reversed, always proceeding from the larger to the smaller 

 chamber, so that in the last, the greatest chamber, the body 

 of the animal thus acquires a smooth foundation, upon which 

 'it can move more freely. In true Nautili also the base of the 

 cells is concave or undulated in the forward direction, \yhile 

 in the Polythalamia it appears without exception to be either 

 quite straight or convex in that direction. This character 

 was also observed by Fichtel and Moll. 



The tabular view which I have given of the Bryozoa, found- 

 ed as it is on the new observations which I have made, is 

 drawn up with special regard to a definite expression of fossil 

 phaenomena, the ancient names of d'Orbigny being mostly re- 

 tained. This very diligent precursor in these studies first laid 

 down a foundation rich in forms and systematically ordered, 

 which may serve for all future investigations, and has given 

 names to families which are well adapted to his purpose; but 

 these I have been obliged to alter, yet not arbitrarily, inas- 

 much as from the difference of our views it became necessary 

 to separate from each other the forms which constitute his 

 families, according as they are either simple Polythalamia, or 

 Polythalamia composing polyparies. 



Since the foregoing pages were drawn out, a newer work 

 by Dr. Ehrenberg has made its appearance, embracing com- 

 munications made to the Berlin Academy, on the continued 

 researches of the author between September 1839 and August 

 1840, and bearing the title, "On the numerous Living Species of 

 Animals found in the Chalk Formation*." Of this very inter- 

 esting publication I had designed presenting an abstract, but 

 having learned that a complete English edition of the work is 

 about to appeart accompanied by the engravings, I now con- 

 fine myself to a few notices immediately connected with the 

 preceding part of this paper. 



In this memoir Dr. Ehrenberg repeats his objections to the 

 views entertained by MM. Alcide d'Orbigny and Dujardin. 

 It has been seen, that to ihe Polythalamia, whose minute and 

 often microscopic calcareous shells compose in inconceivable 

 numbers, and in now nearly 1000 known different forms, the 

 principal mass of chalk rocks and of many sands of the sea, 

 M. d'Orbigny had several years since ascribed an external 

 animal bearing the form of a Sepia, the small shell itself, which 



• Ueber iiock zahlreich jcizl-lebende Thierartcn tier Krcidcbildung, pp. 94, 

 with four plates, Berlin, 1840. 



t In tile Scientific Memoirs of Mr. R.Taylor. Its publication cannot 

 fail to prove very acceptable to British Naturalists in general. 

 2G2 



