EXPLANATION OF PLATES 37. 38. 



59 



a. Exterior dorsal margin. 



b. Back view of the shell. 



c. Transverse section of shell. 



The figures in this Plate are selected to exemplify some 

 of the various manners in which the shells of Ammonites 

 are adorned and strengthened by ribs, and flutings, and 

 bosses. In Vol. I. p. 340, instances are mentioned of similar 

 contrivances which are applied in Art to strengthen thin 

 plates of metal. Workers in Glass have also adopted a 

 similar expedient in their method of fortifying small wine 

 flasks of thin glass, made flat, and portable in the pocket, 

 with a series of spiral flutings passing obliquely across the 

 sides of the flask, as in many of the flattened forms of 

 Ammonite. Similar spiral flutings are introduced for the 

 same purpose on the surface of thin glass pocket smelling- 

 bottles. In other glass flasks of the same kind which are 

 made in Germany, the addition of bosses to the surfaces 

 of the flat sides of the bottles, produces a similar double 

 result of ornament and stren2;th. 



Plate 38. V. I. p. 347. Note. 

 Air chambers of Ammonites heterophyllus, filled with 

 Lias, and shewing; in a remarkable deo;ree the effect of the 

 undulating course of the edges of the transverse plates 

 beneath the flat sides of the outer shell. 



