258 GEO. H. HORN, M. D. 



Species occur in each of the genera on both sides of the continent 

 except Pht/conomufi, which occurs on the sea-shore of the Pacific only. 



The sequence of genera in the above table is different from that 

 adopted in the " Classification," as it seems to show a certain relation- 

 ship with the Nitidulidge through Bactridium, and to the Lathridiid?e 

 through Monotonia, the other genera being very natural intermediates 

 between these two. 



MONOTOHA Hbst. 



Head slightly prolonged behind the eyes, then suddenly constricted. 

 Antennae ten-jointed, last joint suddenly broader, ninth joint not wider 

 than the preceding. Pjlytra with rows of punctures each bearing a 

 short hair. Intercoxal process broad, feebly rounded in front, first 

 vehtral segment without coxal lines. 



The species of this genus are much more difficult to separate than 

 those of any other in the family, on account of the similarity of form 

 and sculpture and the tendency to become coated with extraneous 

 matters, which adhere to and hide to a greater or less extent the 

 surface and are troublesome to remove. 



The head is usually densely punctured, the punctures coarse and 

 deep, each bearing a very short whitish hair. 



The thorax is similarly sculptured, and has near the base two foveas 

 more or less marked, often very feeble. One species has four excava- 

 tions. In shape there is a moderate variation. The usual form is 

 narrowed in front, but species occur with the sides parallel or even 

 slightly convergent posteriorly. The anterior angles may be promi- 

 nent or not. The hind angles are also variable, usually rectangular 

 and moderately prominent, often feeble or even obliterated. 



The elytra vary somewhat in sculpture. One species has simple 

 punctures, the others have punctures more or less muricate, especially 

 near the base. 



The underside of the body varies in sculpture from a coarse 

 punctuation almost to smoothness and is a useful character in de- 

 fining species. 



The following table gives in brief the principal characters of the 

 species and will enable them to be easily distinguished. 



Antennge slender, joints 4 — 9 longer than wide pro<Itlcta. 



Antennae stouter, joints 4 — 9 submoniliform 1. 



1. — Metasternum densely punctured at middle and sides 2. 



Metasternuin nearly smooth at middle and posteriorly 6. 



2. — Head rather deeply obliquely impressed on each side picipes. 



Head regularly convex, not impressed .3. 



