6 



SHELL GALLERY. 



Economic 

 uses. 



Geological 

 history. 



General 

 distribu- 

 tion. 



Helix desertorum. 

 (See black table-case 1.) 



It must have come out of its shell in the interval, and finding it 

 was unable to crawl away, had again retired within it, closing the 

 aperture with a new epiphragm, but leaving traces of slime upon 

 the tablet, which led to its immersion in water and subsequent re- 

 vival, having passed a period of four years in a dry museum with- 

 out the smallest particle of food. 

 It lived till October, 1851, then 

 became torpid, and was found to 

 be dead in May, 1852. The 

 actual specimen is here figured. 

 Fig. 1. 



The economic uses of molluscs 

 to man are manifold, and will be 

 mentioned in the course of the de- 

 scription of the several families ; 

 but here may be the place to direct the attention of visitors to 

 side table-cases B and D at the side of the room, containing some 

 specimens of articles manufactured from shells, such as cameos, 

 flowers, bracelets, brooches, &c. 



Mollusca made their appearance on the globe at a very early 

 epoch in the history of the development of animal life, a large 

 number of Cephalopoda, such as Lituites, Orthoceras, &c., being= 

 found in the oldest Palgeozoic formatious. Probably all these 

 belonged to the Tetrahranchia, of which one descendant only, the 

 Pearly Nautilus, has survived to our period. Some Gastropods 

 and Bivalves coexisted with those ancient Tetrabranchs ; but these 

 types abounded more in the later geological epochs, many Tertiary 

 forms being undistinguishable from species Which now exist. 



The greater number of Mollusca are inhabitants of the sea, 

 some passing their whole life at the surface hundreds or thousands 

 of miles away from land ; others at the bottom of the ocean at all 

 depths, some having been dredged at five miles from the surface. 

 Many are found in much shallower Avater, and a large number 

 between tide-marks. Elvers and lakes furnish an immense variety 

 of forms, and vast numbers live on land in all situations — on 

 mountains, in valleys, forests, and deserts. 



Molluscs are generally either animal or vegetable-feeders, the 

 former preying principally upon other members of their own class. 



& Son. 



From Woodward's ' Manual of the Mollusca,' published by Lockwood 



