206 ADEPHAGA. [Dl/tisCUS. 



face pitchy with the margins of elytra and the whole border of thorax 

 yellow, scutellum yellowish, elytra with very fine yellow longitudinal 

 lines which are sometimes plain, sometimes almost obsolete ; under side 

 testaceous with the sides of abdomen spotted with black ; antemife and 

 legs testaceous ; prosternal process short ; coxal processes elongate and 

 acuminate ; male shining Avith elytra strongly punctured towards apex, 

 female dimorphic, sulcate and dull, or as in male except that the thorax 

 is more closely and finely punctured in the middle. Long. 25-28, lat. 

 14-15 mm. 



Very local, but sometimes Bot uncommon where it occurs; found in Highland 

 lakes in Scotland in the Moray, Clyde, and Argyle districts ; it is not uncommon 

 in Mull ; Ireland, Donegal, in tarns ; taken in some numbers by Mr. Somerville. 



D. dixnldiatus, Berg. The largest of our species, and at once dis- 

 tinguished irom all the others except D. punctulatus by having only the 

 side margins of the thorax broadly yellow ; with the latter species it 

 need hardly be compared, being a great deal larger and having the under- 

 side ferruginous with the metasternum pitchy in the middle ; the elytra 

 are somewhat widened behind ; the thorax has a very narrow light border 

 in front ; antenna and legs red, posterior tarsi black ; prosternal process 

 rather elongate, acuminate ; coxal processes blunt; male shining, female 

 always sulcate, the sulci reaching hardly beyond middle. Long. 32-37, 

 lat. 17-18 mm. 



This species used to be locally abundant in the Cambridgeshire and other fens, but 

 of late jears has become exceedingly rare : the last specimen taken in Britain was 

 found three or four years ago in Askham Bog, York, by the Rev. W. C. Hey. 



In Dr. Power's collection there is a specimen of Cyhister Roeseli 

 labelled as follows : "Found Sept. 30th, 1826, in a puddle at "Walton, 

 Essex, by J. Dane, Esq., who gave it to H. Griesbach, from whose col- 

 lection it came ; this is the specimen alluded to by J. F. Stephens on 

 which it was introduced;" this species cannot be admitted into our lists 

 without further confirmation, but there is no reason why it should not 

 occur, as it is found in Northern France and Belgium, and other species 

 that have long been erased from our lists have been confirmed afterwards 

 (e. g. Harx>alus caheatus, found by myself at Bridlington after an interval 

 of more tlian fifty years). C. Roeseli resembles a large Dytiscus, but is 

 much more depressed, and has the elytra widened behind ; the sides of 

 the tliorax are testaceous, and the elytra have a broad light band near 

 margin attenuated towards apex and separate from the side margin ; the 

 body underneath is testaceous. Long. 34, lat. 18| mm. 



HYDATICINA. 



This tribe comprises two genera, one, Prodaticus, from India, con- 

 taining one species, and the other Hydaticus, which is distinguished by 

 the very unequal claws of the posterior tarsi. 



