AMMONITES— ZOOLOGJCAI.. ETC. 



83 



never attain two centimetres in diameter, though they al- 

 ways exceed five ; whilst, 4th. A. Clementinus, LeivesiensiSy 

 perampluSf clypeiformis, Bidichotomus, Rhotomagensis, 

 rusticus, ^c, arrive at a diameter of thirty centimetres. 

 There are some amongst them, which, like A, Lewesiensis 

 attain a metre in diameter. Thus, when regarded in this 

 point of view, each species of Ammonite appears to have a 

 fixed limit of growth ; otherwise all would arrive at the same 

 size, which is not the case. 



I have mentioned that the size which is proper to the spe- 

 cies, has no connection with the external modifications or 

 the ornaments with which they are provided. To convince 

 oneself of this fact, it is only necessary to compare the 

 smallest ^. pretiosus, striaticulcatus, verrucosus, asperri- 

 nus and Braviasianus, the ornaments of which are exceed- 

 ingly complicated with larger species which are destitute of 

 them, as A. peramplus, clypeiformis and Lewesiensis, 



I have also stated that the complication of the foliations 

 of the septa is not always in connection with the size of the 

 species. The numerous foliations of A. Belus, Calypso, 

 picturatus, h^c., will prove this, as their parts are exceed- 

 ingly complicated, and thus nevertheless of small size. 



\To he continued?^ 



Tabular View of the Melting Points of Metals, as deter^ 

 mined by different Expterimenters. By Professor Gordon, 

 of Glasgow, communicated by Theodore F. Moss, Esq, 



Tin melts at 



228" centigrade 



according to 



Crichton 



do. 



267'^ 



do. 



do. 



Guyton 



do. 



228*^ 



do. 



do. 



Rudberg 



do. 





do. 



do. 



Kupffer 



do. 



222.5" 



do. 



do. 



Ehrmann 



Bismuth 



246" 



do. 



do. 



Crichton 



g2 



