THE GEOLOGIST. 



OCTOBER, 1860. 



GEOLOGICAL L 0 C ALIT I E S.— Ko. 1. 

 EOLKESTONE. 

 By S. J. Mackie, F.G.S., ¥\S.A. 



(Continued from age 32 7. J 



Of all tlie Gault fossils, tlie Ammonites take precedence both for 

 beauty and nmnber; and, holding as tlie Cephalopods do the highest 

 rank of molluscous animals, we cannot but view their extraordinary 

 variety in this deposit with singular mterest. If, therefore, we dwell 

 here somewhat at length on their general classification, we could 

 scarcely choose a more fitting occasion. 



As ordinarily seen in collections, the Gault Ammonites appear to 

 be all more or less of diminutive size. Few exceed two inches in 

 diameter ; many are little more than an inch ; while one of three 

 inches would be looked upon as a fine individual. 



These specimens are, however, for the most part only the central 

 whirls solidified or hardened by interior walls, or in-fillings of iron- 

 pp'ites. In the Gault itself Ammonite- shells of far larger size — 

 commonly of six or seven inches across, sometimes more than a foot 

 — are not merely frequent, but extremely abundant, although, from 

 the fragile state of the main mass, they are commonly cleft to 

 pieces in breaking out the central pyritous cores without attracting 

 observation. 



Even if collected, theu* tendency to peel away from the matrix 

 VOL. III. 2 Y 



