336 COLEOPTERA OP NORTH AMERICA. 



Tribe VII. MESOSltfl. 



This tribe has but a single representative, Syna^hoetajjuexi, in 

 California ; a rather large, stout insect clothed with gray pubes- 

 cence ; antennae aunulated, prothorax with two black vittoe, and 

 elytra each with two angulated black bauds. 



The front is large and quadrate, labral support large, coriaceous ; 

 vertex deeply channelled; mouth large, palpi slender, pointed; eyes 

 finely granulated, almost divided, lower lobe nearly quadrate ; 

 antennae longer than the body iu 1 , shorter in 9 , scape long 

 with an oblique apical cicatrix ; prothorax with a very obtuse 

 lateral tubercle just behind the middle ; elytra wider than thorax, 

 nearly parallel, depressed on the back, suddenly iuflexed at the 

 sides, broadly rounded behind. 



Front coxae angulated, closed behind, with large trochantin ; 

 middle coxal cavities open externally ; mesosternum protuberant ; 

 metasternum a little longer than the 1st ventral ; 2-4 segments 

 nearly equal, 5th in $ somewhat emarginate, longer, channelled, 

 and more deeply emarginate in 9. Legs rather short, equal, 

 middle tibiae without tubercle or sinus on the outer margin ; tarsi 

 short, and broadly dilated, claws divergent. 



The species of this tribe resemble in appearance the stouter forms 

 of the next two tribes, but differ by the strongly augulated front 

 coxal cavities. 



Tribe VIII. ACANTHODERIM. 



With this tribe commences a long series of genera having the 

 claws divaricate ; the front is large, quadrate, vertical, mouth 

 large ; support of labrum large, coriaceous; palpi slender ; anten- 

 nae variable, sometimes excessively long in both sexes, sometimes 

 (sub-tribe Acanthoderini) hardly longer than the body ; vertex 

 not much excavated, eyes finely or somewhat coarsely granulated, 

 lower lobe nearly quadrate. Prothorax armed or not on the sides, 

 position of spine variable. Elytra rounded or truncate at tip, 

 usually flattened on the disk, rarely (Dectes) cylindrical. 



Front coxal cavities rounded, closed behind, usually by a broad 

 corneous space, sometimes (Dectes) very narrowly, so as almost 

 to appear open. Middle coxal cavities closed externally ; legs 

 moderate, thighs usually strongly clavate, middle tibiae with a 

 tubercle on the outer margin, hind tarsi sometimes short, some- 

 times elongated. 



