COLEOPTERA. 391 



the three last form an almost solid club composed of five dis- 

 tinct joints, the last of which is large, with two stout terminal 

 hooks. The body is thick or convex. The thorax is less 

 rounded, and most commonly terminates on both sides in acute 

 angles. 



The principal type of this tribe is the genus 



Dryops, Oliv., 



Or that of Parnus, Fab., which is divided in the following manner. 



1. Those whose antennae, never much longer than the head, are 

 composed of from ten to eleven joints, which, from the third, form 

 an almost cylindrical or slightly fusiform club, arcuated, and some- 

 what serrated. 



Potamophilus, Gerrm Parnus, Fab. 



The Potamophili, which, ignorant of the establishment of this 

 subgenus, we had named Hydera(I), have their antennae exposed, 

 and not received into particular cavities; they are rather longer than 

 the head; the first joint is almost as long as the following ones taken 

 together, and the second short and globular. The palpi are salient, 

 and the mouth is completely exposed as the prsesternum does not 

 project over it, a character in this tribe exclusively peculiar to this 

 subgenus(2). 



Dryops, Oliv. Parnus, Fab. 



In Dryops proper, the antennae, shorter then the head, are re- 

 ceived into a cavity situated under the eyes, and are almost covered 

 by the second joint, which is large, dilated, in the form of an almost 

 triangular palette, and projects in the manner of an auricle, whence 

 the name of Dermeste a oreilles, given to the most common species 

 by Geoffroy(3). The palpi are not salient. 



2. Those in which the antennae, composed of eleven joints, are 

 filiform, or merely a very little thicker near the extremity, and at 

 least nearly as long as the head and thorax. 



(1) Regn. Anim., Ill, p. 268. 



(2) Parnus acuminaius, Fab.; Panz., Faun. Insect. Germ., VI, 8; Dryops 

 picipes, Oliv., Ill, 41, 1, 2. 



(3) Latr., Gen. Crust, et Insect., II, 55; Schoenh, Synon. Insect, I, ii, p. 116. 

 The Dryops Dumerilii presents some differences in the length of the legs, the 

 form of the antennx and thorax, which have induced Doctor Leach to form a se- 

 parate genus Dryops for it. The other species re-enter Parnus. 



