175 



three of these shells to the reader's notice, on account of 

 some particular circumstances in their history. 



Miliolites saxorum, Lam. (PI. vi. fig. 18.) This minute 

 species of fossil shell is known to form the principal part of 

 the masses of stone in some of the quarries in the neigh- 

 bourhood of Paris, Versailles, Champagne, &c. The recent 

 shell has been found on Fucus, near the island of Corsica ; 

 and by Mr. Boys and Mr. Walker on our coasts, and was, 

 by the latter writer, named serpula subovalis intorta. * 

 It was also mentioned by Mr. Montague as vermiculum 

 i /i tor turn. 



Cornu ammonis ariminiense, Plane. (PI. vi. fig. 19,) is 

 the shell which Plancus and others classed with the cornu 

 ammonis, considering them as the recent shells of this 

 genus ; but the discovery of fossil microscopic shells exactly 

 analogous with the minute recent ones has shown their 

 correspondence with each other, and that they are entirely 

 different from the shells of the genus ammonites. 



Gyrogonites. A spheroidal hollow fossil, of the size of a 

 middling pin's head, having two poles, in which terminate 

 five tubules turning from right to left, and making one 

 revolution and a half round the spheroid. PI. vi. fig. 20. 



M. Leman has been enabled to discover a close agree- 

 ment between the form and structure of this fossil and of 

 the seed-vessel of a small aquatic plant, chara vulgaris, 

 which has been described and figured by Gaertner. 



These three last fossils are figured of their natural size, 

 and as magnified by the microscope. 



It may not be improper to observe, that the great 

 numbers in which these and various other minute fossil 

 shells have been found in different strata, render them very 

 desirable objects of research to the scientific inquirer. 

 There are several circumstances by which the oolitic bodies, 



* Testae, minut. rarior. Tab. i. fig. 1. 



