292 Dr. J. L, Leconte on the Systematic Value 



teguments are perfectly chitinized, the elytra never abbreviated 

 or wanting; the anterior coxse are always completely enclosed; 

 the ventral segments, usually five, never exceed six in number. 



The plan of degradation, in passing from the higher to the 

 lower forms, is by the extension of the longitudinal axis of the 

 body, in its anterior half; this is usually most strongly mani- 

 fested in the head, and exhibited not only by the length of the 

 beak, but by the conformation of the lower floor of the mouth. 



Commencing with those Curculionidse (Adelognathi, Lacor- 

 daire) in which the mentum fills the gular emargination, as in 

 the higher Tenebrionidse, we find a gradual lessening in size of 

 the mentum, itself becoming supported upon a broad, short, 

 gular peduncle, permitting the maxillse to become visible (Pha- 

 nerognathi. Cohort I., Lacordaire) ; next, the gular peduncle 

 becomes elongated and bilobed, receiving the mentum, now re- 

 duced to very small size, between its lobes (Phanerognathi, 

 Cohort II. and also Brenthidse and Anthribidfe). 



Having, in the continuance of my work on the Classification of 

 the Coleoptera of North America, recently commenced a critical 

 study of our Ehynchophora, I became aware of the impossibility 

 of intercalating them between the Heteromera and Subpenta- 

 mera, and am now convinced that they represent a special type, 

 which must be isolated from all other types of Coleoptera, pos- 

 sessing a systematic value equal to all the others combined. 



In seeking for the characters which should define this type, 

 I observed a remarkable difference in the arrangement of the 

 pieces of the under surface of the prothorax, heretofore over- 

 looked, and, so far as I know, confined to this particular type. 



In other Coleoptera the prosternum is either extended behind 

 the anterior coxse, so as to form part of the hind margin of the 

 segment, thus coming in contact with the mesosternum, or it is 

 cut off between the coxse, and in this case (as in many others) 

 the coxal cavities are open behind : in the few exceptions 

 [Derodontus, Dacoderus) in which the coxa are contiguous and 

 the cavities closed behind, the prosternum still extends behind 

 the coxse to the hind margin of the segment, as is shown by 

 the short sutures separating the epimera from the medial piece 

 of the prosternum. 



I have represented these modifications of form in the adjoin- 

 ing woodcuts. Fig. 1, under surface of prothorax of a Carabide 

 [Pasimachus); the coxal cavities are closed, and the epimera and 

 episterna well defined. Fig. 2, ditto of a Scarabseide [Lackno- 

 sterna) ; the coxse are transverse, the cavities closed, the side 

 pieces not distinct. Fig. 3, ditto of Cucujus ; coxal cavities open 

 behind, side pieces not distinct. Fig. 4, ditto of Telephorus ; 

 coxal cavities confluent, and open behind. 



