On Aquatic Carnivorous Coleoptera or Dytiscida. 503 
The shining surface and large meshes of the reticulation are very characteristic ; 
when a careful examination is made, it is seen that in the middle of these meshes 
(not on the lines thereof as in most other species), there are excessively minute 
punctures. ; 
Colymbetes nitidus, Say. (Tr. Am. Phil. Soc. II. p. 98) is referred to this species 
on the authority of Crotch. 
North America, (Massachusetts). 788. 
686. Agabus planatus,n.sp.—em. Ovalis, haud convexus, pernitidus, nigro-piceus, 
colore subtus paulo dilutiore, antennis pedibusque rufis, elytris pone medium versus 
latera lineola, et ante apicem gutta testaceis ; supra undique conspicue reticulatus, 
reticulis magnis ; prothorace margine laterali crasso. Long. 9, lat. 5 m.m. 
I have seen but a single individual (?) of this species, which seems to be very 
closely allied to Agabus obtusatus, but is a good deal larger, and has a much broader 
lateral margin to the pronotum. 
This is perhaps the insect considered by Crotch (Tr. Am. Ent. Soc., 1873. p. 41 7), 
to be a female variety of Agabus semivittatus, Lec. 
North America. 789. 
687. Agabus brevicollis, Lec., M.C.—Late ovalis, subdepressus, vix nitidus, niger, 
antennis rufis, pedibus piceis ; elytris densius profunde reticulatis, pone medium 
versus latera guttula ferruginea. Long. 10, lat. 62 m.m. 
I have seen but a single individual, a male in very decayed condition, of this very 
distinct species; it is of a very broad flat form, with the thorax continuing the 
outline of the elytra with very little interruption, the lateral margin of the thorax 
is broad and but little raised ; this male has the front and middle tarsi moderately 
incrassate and furnished beneath with glandular hairs, the claws are broken. 
North America, (California). 802. 
Group 4. 
The single (European) species forming this group has the characters similar to 
those of the highly developed members of group 2, except that the swimming legs 
are highly developed, being short and thick. 
688. Dytiscus brunneus, Fab., Agabus brunneus, M.C.—Ovalis, latiusculus, sa 
convexus, nitidus, levis, subtus niger, capite prosternoque ferrugineis, medio nigris, 
