Casey — Observations on the Staphylinidae. 205 



tudinal ridges. The medial carina is, however, obsolete in 

 certain forms indicated below as subgenera of Tachyusa for 

 present convenience. The eyes are well developed, the an- 

 tennae long, gradually incrassate distally, the neck rather 

 wide, the prothorax obtrapezoidal, wider than long, with the 

 hind angles more than right but always very distinct and not 

 in the least blunt. The elytra are well developed, each ob- 

 lique at tip, the external sides strongly projecting posteriorly, 

 forming a strong sublateral sinus and the legs are long and 

 slender. The sexual characters are remarkable, the pronotum 

 in the male being evenly convex or nearly so, while in the 

 female it is generally broadly and strongly impressed along 

 the middle, and, besides, is frequently more opaque, due to 

 a minute reticulation which may not appear at all in the male; 

 the latter sex has the sixth ventral plate minutely and angu- 

 larly to :fifebly and broadly sinuate at tip as in Gnypeta. The 

 homogeneity of the genus renders a satisfactory tabular state- 

 ment of the differential characters much more difficult than 

 in Gnypeta, but it is hoped that the following table may aid 

 in the identification of the rather numerous species : — 



Abdomen highly polished, extremely remotely and rather leas finely punc- 

 tulate; mesosternal process wider than usual, truncate or rounded at 

 tip but attaining the raetasternum 2 



Abdomen minutely and closely punctulate, alutaceous or pruinose; species 

 smaller 3 



2 — Antennae very slender, only very feebly incrassate distally. Body stouter 

 than usual, polished, piceous-black, the legs and antennae blackish, the 

 tarsi paler, the basal ventrals somewhat rufescent ; vestlture inconspic- 

 uous; head well developed, orbicular, minutely, sparsely punctate, the 

 vertex broadly impunctate and feebly concave toward the middle; an- 

 tennae extending to the tips of the elytra, the second and third joints 

 much elongated, the latter rather longer than the first, the tenth dis- 

 tinctly elongate; prothorax only very slightly transverse and evidently 

 wider than the head, scarcely a fifth wider than long, the sides narrowly 

 rounded anteriorly, thence moderately converging and almost straight 

 to the base, the surface finely, granularly and somewhat closely punc- 

 tured, not reticulate, broadly concave along the median line in the fe- 

 male, very narrowly and obsoletely so in the male; elytra about two- 

 fifths wider and longer than the prothorax, the humeri moderately ex- 

 posed, the suture not impressed behind the scutellum, the punctures fine, 

 not close -set and asperulate; abdomen highly polished; hind tarsi about 

 two-thirds as long as the tibiae, the basal joint not as long as the next 

 two combined ; sixth ventral of the female broadly rounded, very feebly 



