280 GEO. H. HORN. 



the inetasternal prolongation. From this we have gradually a larger 

 extent developed through Dactyl, advectum to the ordinary arrow- 

 head type so often seen, of which the pentagonal form of Crypto- 

 pleuruni et al. is plainly a further extension. 



In the Cyclonotum series alone the metasternuni is so extended as 

 to practically form the entire sejiaration of the middle coxae, and in 

 Phpenonotum is still more prolonged. In the latter genus and Dad. 

 advectum the structure imitates that of Tropisternus and Hydrocharis 

 in form, although of different com])osition. 



The prosternum is nsnally elevated along the median line in a 

 carina which varies in height from scarcely more than an elevated 

 line in many Cercyon, to a lamina of considerable elevation in Dac- 

 tylosternum. 



In the Megasternum group, however, the prosternum is rather 

 broadly elevated at middle, forming an area of varying shape, which 

 extends between the front coxse and is on the same plane with the 

 meso-metasternal surface. 



The form of the metasternal episterna does not seem to have at- 

 tracted attention. It will be observed in the Cyclonoti that this por- 

 ti(m attains its fullest development in width. In the Cercyones the 

 episternum is narrower, but with parallel sides, while in the ^lega- 

 sterni the inflexed elytra cover a portion of the episternum, so that 

 it seems very narrow, and in Crvptopleurum is concealed in front. 



In several species of Cercyon the metasternal area is extended by 

 a sinuous oblique line directed toward the anterior angles. The 

 ineaning of this is fully explained in Cryptopleurum in which the 

 entire area thus limited is abruptly, although slightly, elevated above 

 the I'emainder of the metasternal area. PI. ix, fig. 9. 



The first ventral segment has a distinct carina in all the genera, 

 except Cyclonotum and Phsenonotum, and in these it will be ob- 

 served there is no distinct prosternal carina. Phpenotypus has no 

 distinct prosternal carina, but a well marked ventral carina. 



The elytra are extended beyond the lower margin of the body in 

 all the Cyclonoti, in the Cercyones the acute edge of the elytra is the 

 true margin of the body, while in the Megasterni the elytra have no 

 Avell defined acute edge and clasp, the body concealing the metaster- 

 nal episterna in part and without distinctly discernible epipleuriB. 



There are other characters of note which seem to have restricted 

 value, these will be mentioned under the genera to which they belong. 



