88 COLEOPTERA OF NORTH AMERICA. 



thorax, connate, rounded, not convex, with nine dorsal furrows, 

 and no marginal one; the apex is slightly sinuate. 



The surface is rough, without lustre, and moderately coarsely 

 punctured. 



This very singular insect is found in northern California, pro- 

 bably near the Sierra Nevada; of its habits nothing is known. 



Fam. IV.— DYTISCIDAE. 



Mentum deeply emarginate, broad! y toothed in the middle; 

 lobes somewhat acute; sides rounded, converging in front; 

 gular suture distinct; ligula large, quadrate, corneous. 



Maxillae with the outer lobe biarticulate, the inner curved, 

 acute at the apex, ciliate internally. 



Eyes rounded, never emarginate. 



Antennae inserted under the front, behind the base of the 

 mandibles, glabrous, polished, usually filiform, 11-jointed 

 (rarely 10-jointed). 



Prothorax with the epimera and episterna distinct ; pro- 

 sternum compressed, produced behind and fitting into a cleft 

 or emargination of the metasternum; anterior coxae protected 

 behind by the mesosternum, subcorneal. 



Metasternum short, pointed behind, but very closely con- 

 nate with the posterior coxae. 



Posterior coxae very large, usually oblique, contiguous at 

 the inner margin, reaching the side of the body, entirely 

 cutting off the ventral segments from the metathorax ; inter- 

 nally with a small dilatation for the insertion of the legs, or a 

 broad plate (Haliplini) extending over their whole surface, 

 and also covering the greater part of the abdomen. 



Abdomen with six ventral segments, the three anterior 

 ones connate, the sixth rounded at tip, usually permitting 

 the seventh internal but corneous one to be slightly visible. 



Legs ciliate with long hairs, posterior usually compressed, 

 elongated, formed for swimming; tarsi 5-jointed, the fourth 

 joint of the anterior and middle tarsi sometimes obsolete. 



In this family are contained aquatic carnivorous insects, having, 

 as will be seen by the above characters, a close relationship to 

 Carabidse, and in fact only differing by the form of the posterior 

 coxa?, and the natatorial legs. The particular portion of the Cara- 

 bidae which approaches most nearly these insects is found in the 



