STAPHYLINID.E 215 



Thinusa robustula n. subsp. General form, coloration and sculpture 

 as in fletcheri but a little smaller in size and with the pubescence shorter, 

 more even and less bristling; head similar, the punctures more distinct, 

 similarly narrowly parted along the median line, the antennae similar 

 though somewhat shorter, the joints from the fourth slightly more 

 transverse, the third more pedunculate at base; prothorax shorter and 

 sensibly more transverse, otherwise nearly similar; elytra similar though 

 with much shorter and more decumbent pubescence; abdomen similar 

 though slightly more shining, with the punctures somewhat finer and 

 not quite so close-set. Length 2.1 mm.; width 0.5 mm. British Columbia 

 (Metlakatla), Keen. 



The differences as announced above hold true and constant, 

 as far as the two examples of robustula and four of fletcheri before 

 me are concerned; they indicate perhaps, that the latter form has 

 probably been modified by reason of its insular habitat, during a 

 comparatively short period of isolation. Inferences of this kind 

 are, however, nothing more than speculative; the differences be- 

 tween the two forms are real and readily observable. 



Tribe HYGRONOMINI. 



The genera of this tribe are very limited in number and character- 

 ized by having only four joints in all the tarsi. There is an inter- 

 esting group, highly developed in subarctic North America, having 

 peculiarly contorted tarsal claws, which seems to be wholly un- 

 represented in the palaearctic fauna, the genus Hygronoma differing 

 very much in tarsal structure, as well as in other ways. A careful 

 survey of the material in my collection shows that there are five 

 generic or subgeneric sections of this group, which may be defined 

 as follows: 



Form nearly as in Falagria, rather stout, with much narrower head and 

 prothorax, the antennae well developed; neck more than half as 

 wide as the head; infra-lateral cephalic carinae wholly wanting; 

 only the first three abdominal tergites impressed at base, the im- 

 pressions subequal, sharp and sculptureless; basal joint of the hind 

 tarsi fully as long as the next two or longer; color black. Atlantic 

 to Pacific Bamona 



Form linear; coloration nearly always pale 2 



2 First four tergites impressed at base; neck well defined, the head 

 constricted at base; infra-lateral carinae wanting or vestigial; elytra 

 well developed and long; size moderate to small 3 



First tergite deeply impressed, the second broadly and feebly, the others 

 unimpressed; neck not defined, the broadly truncate base of the 



