258 SUPPLEMENT ON THE CARNIVOROUS FAMILY 



that they arc narrower at the apex than the base, yet, 

 nevertheless, in some instances, as in certain species of Lycus, 

 the reverse is a fact. In other instances, their width is 

 every where the same. Sometimes their form is convex, 

 and sometimes extremely flat. 



The mode in which these peculiar organs, of which we are 

 treating, are often sculptured, is very curious, and often very 

 beautiful. Some are marked with striae or furrows, others 

 M'ith slightly raised ridges. That these elevations and de- 

 pressions, not only in the elytra, but on other parts, are not 

 intended for the mere purposes of ornament, Mr. Kirby 

 maintains, with much appearance of reason. " By means of 

 these," remarks that gentleman, " many important purposes 

 that do not at first sight strike the observer, may be served, 

 such as giving firmness to the crust in those places where it 

 is most wanted ; diminishing its power of resistance in 

 others, so that it may yield somewhat to the action of the 

 muscles ; increasing or deducting from the weight of the 

 body, so as to produce a proper equipoise during its motions, 

 whether on the earth, in the air, or in the water. The 

 depressions of the outer surface of the crust, in many in- 

 stances, produce an elevation of it in the interior, and so 

 afford a useful point of attachment to certain muscles. This 

 observation seems more especially applicable to those exca- 

 vations which are common to particular tribes or genera; 

 thus the dorsal longitudinal channel to be met with on the 

 prothorax of most of the ground beetles, (Eutrechina,) on 

 the inside of the crust, has a corresponding ridge. In 

 Locusta Duwy also, a Brazil locust, the same part has four 

 transverse channels, corresponding with which, on the inside, 

 are as many septa or ridges to which muscles are attached ; 

 and those larger impressed puncta denominated puncfa or- 

 dinaria, which distinguished the same part in Geotrupes 

 and many of the scarahceidce within are elevated so as to 



