108 COLEOPTERA OF NORTH AMERICA. 



5. Pygidium exposed. Ptilium. 



Pygidium concealed. Ptenidium. 



Tribe II.— TRICHOPTERYGII^I. 



Anteniiffi elongate, ll-jointed. li. 



Antennfe short, 9-jointed. Limulodes. 



2. Prothorax not constricted or contracted behind ; antennae regular, joints 



3-7 slender. 3. 



ProtUorax constricted behind. (i. 



Prothorax narrowed behind, not constricted. 7. 



3. Abdomen with seven ventral segments. 4. 

 Abdomen with six ventral segments. H. 



4. Prothorax greatly dilated, hind coxse widely distant. * Actinopteryx. 

 Prothorax moderately dilated, hind coxse moderately distant. Pteryx. 



5. Hind coxse very widely distant ; mesosternum scarcely carinate ; color 



pale. Ptinellodes. 



Hind coxae distant ; mesosternum carinate. Trichopteryx. 



6. Elytra long ; mesosternum carinate ; middle coxse distant ; hind coxie 



not very distant ; color dark. Smicrus. 



Elytra short ; mesosternum not carinate ; middle coxse contiguous ; color 



pale. Ptinella. 



7. Elytra short ; hind coxse laminate. Nephanes. 



Fam. XV.-HYDROSCAPHIDAE. 



Body very small, elongate, narrowed behind, convex ; 

 abdomen extending beyond the elytra. 



Antenna 8-jointed, gradually thicker externally, last joint 

 long, with two slightly marked rings near the tip. 



Maxillaj with but one lobe, palpi 4-jointed; 1st and 4th 

 joints short, 2d and od long, the latter a little wider than 

 the 4th. 



Labial palpi short, 3-jointed, joints diminishing in length 

 and thickness. 



Hind coxte laminate; legs short, tarsi 3-jointed, claws 

 toothed at base. 



Abdomen with six free segments : 1st and 6th each longer 

 than the other four united, at the end with several fimbriate 

 narrow acute processes, which serve as swimming organs. 



Elytra truncate behind, wings narrow, fringed with long 

 hairs. 



* This genus has not yet been found within our faunal limits. 



