Mr. Bennett on the Anatomy of the Thorax In Insects. 391 



thickened, especially on the sides of the extremities a"nd the outer 

 lip, where it is slightly margined ; mouth rather large, whitish 

 violet ;•■ teeth small, blunt, nearly equal, those in the front of the 

 inner lip being only a little larger ; columella smooth, concave ; 

 inside purple ; axis ■*•§, diameter T 6 ^ of an inch. 



When young the shell is ovate, purplish-grey, with three broad 

 dark purple bands, and scattered with very small fulvous yellow 

 specks, and the base is whitish Violet, with or without a few 

 scattered minute blackish-purple specks. 



When worn it is brown, with three darker bands, and an irre- 

 gular dorsal spot ou the back, and a pale violet spotted base. 



This is a well known and not uncommon species, although it 

 has not been well figured in its perfect state. The figures of 

 Martini and of the French Encylopasdia, appear to be from worn 

 specimens, which probably misled Mr. Swainson, and induced 

 him to describe it as new. 



\To be continued.'] 



Art. XL VI. General Observations on the Anatomy of the 

 Thorax in Insects, and on its Functions during Flight.* 

 By E. T. Bennett, F.L.S. and Member of the Zoo-' 

 logical Club of the Linnean Society. 



The thorax or trunk is that portion of the body of an insect 

 which is articulated in front to the head, and posteriorly to the 

 abdomen. Entirely subservient to the purposes of motion, the 

 whole of the organs destined to support the animal in flight, in 

 walking, or in swimming, are attached to its various surfaces. 



In all insects the thorax is divided into three segments, corres-. 

 ponding with the three pairs of legs with which the animals of 

 this class are universally provided. The first of these segments 



* Extracted chiefly from the " Essai sur le Vol des lnsectes, par J. Cha-. 

 brier." Mem. du Museum d'Histoire Naturelle, * 



