on the Organic Compositiu7i of Chalk and Chalk Marl. 30'J 



bled in si?igle roros, from the Red Sea and the Mediterranean. 

 The two subjects represented in this Plate were collected by 

 me in the year 1823, and it is peculiarly interesting, through 

 my newly-discovered method of observing*, to have been 

 able to see in several divisions of the internal body the 

 remains of the siliceous Infusoria, of which they had made a 

 repast fifteen years before. Fig. 1. Peneroplis planatus, d'Or- 

 bigny, Nautilus planatus of Fichtel and Moll, from the Red 

 Sea. The shells of this animalcule were hitherto only known, 

 but the soft organic animal form which they inclose is here also 

 represented. Fig. 2. Coscinospira Hemprichii, a form from 

 the Red Sea, also found in the Libyan part of the Mediter- 

 ranean, and which was formerly erroneously placed adjoining 

 the Spirula of the Cephalopods, and more recently as con- 

 nected, through Litiiolites nautiloides, with Spirolina. 



Plate III. contains Poli/paries of recent Poli/thalamia assem- 

 bled in many roa:s. This Plate contains the only living ani- 

 malcule of the Polythalamia group, hitherto so far observed 

 as to admit of its classification. The three forms given in 

 this Plate, constructed of many rows of animalcules, may be 

 distinctly associated with the Flustra and Eschara of the 

 Bryozoa, to which, through the well-known L,iumlites and 

 Orbitidites (hitherto ranked with coral animals), they approxi- 

 mate in a convincing manner. Fig. 1. Orbiculus nnmismalis^ 

 from the sea-sand of the Antilles Isles. Fig. 2. Sorites or- 

 biculus =■ Nautilus orbicidus, Forskal, Nummidina {Assili?ia) 

 nitida, d'Orbigny, ? from the Red Sea. The same species 

 lives also in the Mediterranean. In a part magnified 300 

 times we see the animalcule with eight feelers protruding from 

 its cell. In some of the cells may be seen distinct shells of 

 siliceous Infusoria; in others appear oviform globules. Fig. 3. 

 Amphisorus Hemprichii closely resembles the Sorites; but it 

 has cells on both sides bearing single animalcules, and hence 



* The new method of observing is the following : — Place a drop of water 

 upon a lamina of mica, and put into it of scraped chalk as much as will 

 cover the fine point of a knife, spreading it out and leaving it to rest a few 

 seconds ; then withdraw the finest particles which are suspended in the 

 water, together with most of the water, and let the remainder become per- 

 fectly dry. Cover this remainder so spread out with Canadian balsam, the 

 turpentine of the Pinus {Abies) bahamea, and hold it over a lamp until it 

 becomes slightly fluid without froth. A preparation thus made seldom 

 fails, and when magnified 300 times in diameter we see that the mass of 

 the chalk is chiefly composed of minute well-preserved organisms. In this 

 preparation all the cells of the Polythalamia appear at first black with a 

 white central spot, which is caused by the air contained in the cells, which, 

 as is well known, ajjpear under water as annular black bodies; but by de- 

 grees the balsam penetrates into all the single cells, the black rings of the 

 air vesicles disap|)ear, and we recognize all the small cells of the Polytha-; 

 laniian animals, often presenting a very pretty appearance. 



