588 EXTERNAL ANATOMY OF INSECTS. 



In Copris Molossus the en&osternum of the medipectus is 

 represented by a transverse zigzag ridge a between the 

 sockets of the mid-coxee, from which proceeds a pair of 

 branches wide at the base and growing gradually more 

 slender to the extremity 15 , which is attached to the sides 

 of the trunk; in Dytiscus marginalis a pair of slender, ver- 

 tical, straight processes, fitted with a broad cartilaginous 

 plate at their apex, rises from the endosternum, and sends 

 forth a lateral one to the side of the medipectus: and lastly, 

 in Carabus the medifurca is represented by a pair of sub- 

 trianmilar lamince attached to the sides of the trunk. 



3. Postfurca c . This, which belongs to the hind- 

 legs, is the most remarkable of the pectoral processes, 

 and has been noticed by more than one writer d . It is 

 a kind of trident, the branches e of which are acute, and 

 on their upper surface longitudinally concave, elevated 

 on a footstalk f inclined towards the medifurca, consist- 

 ing of two plates, a posterior one supporting the lateral 

 branches, and an anterior or interior one forming a right 

 angle with the other, supporting the intermediate one. 

 This footstalk rises from between the posterior coxae, 

 which appear in the Lamellicorns to ginglymate with it at 

 its base. The middle branch of the trident dips to the 

 sinus of the medifurca. In Dytiscus marginalis the form 

 is different ; for the intermediate branch consists of two 

 parallel pieces, and the lateral ones are dilated into broad 

 vertical plates : the stalk of this is triquetrous, and a tri- 

 ple cartilaginous partition appears to go from its base 

 anteriorly, the lateral ones diverging to the sides of the 



A Plate XXII. Fig. 6. a. ■> Ibid. b. c Ibid. Fig. 5. b. f 



d MacLeay, Horcc Entomolog. 9. Chabrier, Sur le Vol des Ins. 

 c i. 41 7. e Plate XXII. Fig. 5. b b b. * Ibid. c. 



