SCOTT— COLEOPTERA; HYDROPHILIDA, HISTERID A 221 
taken together, joint 2 short but longer than broad, joint 3 narrower, short but also 
longer than its breadth, 4 and 5 very short, 6 very short and transverse, applied to 
the base of the club, joints 7—9 forming a very compact obovate club*. Mallary 
palpi with second joint considerably swollen distally, third jot very slightly swollen 
distally, fourth joint slightly swollen in the middle, and subequal to, or slightly longer 
than the third (owing to insufficiency of material it is impossible to make a preparation 
of the mouth-parts, hence the relative lengths of joints cannot be exactly determined). 
Mentum narrowed in front, scarcely impressed in the middle of the front margin. 
Wings examined in one specimen and found fully developed, about twice as long as 
elytron. Prosternum not carinate in the middle, but with its median portion forming 
an elevated oblong area, finely-margined on either side, with surface shghtly concave 
in front, and with hind margin angularly excised (between the anterior coxze) to 
receive the apex of the elevated part of the mesosternum (see Pl. 14, fig. 22). 
Mesosternum forming an elevated, narrowly ovate, margined area, acuminate in front, 
with surface concave. Metasternwm strongly elevated in the middle, with a marked 
longitudinal impression in the middle of the elevated portion; in front it is only 
slightly produced between the middle coxee, and is depressed, so that the middle of 
the front margin is hidden under the posterior extremity of the elevated mesosternal 
area: the “femoral lines” + are very clearly marked and uninterrupted, reaching to 
the anterior corner of the metasternum: in their front part they are fine raised lines, 
while their posterior portion is formed by the edge of the elevated median part of the 
metasternum. Basal abdominal segment with a median longitudinal carina. Anterior 
tabie with the outer margin bearing about 5 short spines distally, and rounded off 
at the apex. Tarsz 5-jointed, scarcely hirsute, with the basal joint distinctly longer 
than the second. 
Type of the genus: Paroosternum degayanum, sp. nov. 
This minute insect is very closely allied generically to Oostermum Sharp (Biol. 
Centr.-Am., Col. i. 2, p. 112, Pl. 3, fig. 16), but differs from it in the form of the 
sterna. Two species of Ovsternum are known, O. costatwm Sharp (/. ¢.) from Central 
America, and O. sorex (Sharp) from Japan (described as Cercyon sorex, Trans. Ent. 
Soc. London, 1874, p. 418): I have examined specimens of both these and compared 
them closely side by side with Paroosternum. In both genera the middle part of the 
prosternum is distinctly differentiated from the lateral parts, but im Oosternwm this 
middle part has an elevated central longitudinal keel and sloping sides, while in 
Paroosternum it forms an oblong elevated area without a trace of a median keel: 
this is the principal difference and is alone sufficient to separate the genera. The 
oblong elevated table of Paroosternum recalls the prosternum of some Histeridze: in 
the one known species its surface is very slightly concave. The genera are closely 
similar in the form of the mesosternum (the surface of the ovoid area being however 
* As in the Cercyon spp. which I have examined, a kind of transverse ridge near the apex of the terminal 
joint of the club makes it appear as if there were a small fourth joint at the apex. 
+ “Schenkellinien”: see Ganglbauer, Die Kafer von Mitteleuropa, iv. 1, p. 273 (1904). 
SECOND SERIES—ZOOLOGY, VOL. XVI. 29 
