milky and P. septentrionis, possess a great general resemblance, and are not 

 easily distinguished except by comparison of specimens. The first two species 

 are apterous, but septentrionis is furnished with wings, is more parallel-sided, 

 and has a shorter thorax than either of the other species. Assimilis differs 

 from excavatus in having the thorax more convex and more narrowed behind 

 than in excavatus, which is more shining and altogether of a flatter appear- 

 ance. All three species measure about a quarter-inch in length, and are 

 generally, but not always, taken in mountainous districts, excavatus being 

 the commonest and most widely distributed species. I have taken assimilis 

 commonly on Snowdon and on the high moors near Llangollen. 



POGONUS. 



This genus also contains three British species, viz., luridipennis, littoralis, 

 chalceus, all of which are moderately common on the muddy banks of rivers. 

 The species are very easily distinguished as follows : — 



A. Head and thorax green ; elytra yellow. 



Length 3 J lines - ** * — - - luridipennis, 



B. Head, thorax, and elytra bronze. 



Elytra broad and rounded at the sides. Length 2>\ lines - chalceus. 

 Elytra narrow and parallel-sided. Length 3 lines - - littoralis. 



TRECHILAi. 



The British species of this family are distributed among three genera, 

 Trechus, Mpus, and Perileptus. These genera are easily distinguished as 

 follows : — 



A. Length over 1 line - Trechus. 



B. Length 1 line. 



Elytra without strise - JEpus. 



Elytra with striae (although these are faint at sides and apex) - - 



Perileptus. 



TEECHUS. 



This genus contains nine British species, several of which are rare. They 

 are not easily distinguished from one another except by comparison side by 

 side, but the following arrangement will, to a certain extent, be serviceable 

 to a beginner : — 



A. Elytra oblong, with parallel sides. 



1. Elytra red, with a distinct bluish black spot across the hinder por- 

 tion; length 2 \ lines ----- discus. 



2. Elytra red, with a faint darker marking behind the middle ; strise 

 near the suture very fine ; length 2 lines - - - micros. 



3. Elytra brownish without dark spots ; strise near the suture deep ; 

 length If lines - - - - - longicornis. 



