On Aquatic Carnivorous Coleoptei-a or Di/tiscidce. 647 



3I(ts, tiitidus, elytris versus apicem crebrius subtiliusque punctatis. 



Fern., subopaca, prothorace utrinque versus latera subtilissime punctato, elytris 

 ad apicem crebrius subtiliter punctatis, punctis sublateralibus majoribus conspicuis. 



In the male of this sjDecies the small palettes of the front tarsi remain quite 

 rudimentary and undeveloped, being no larger than those of the intermediate feet. 



The colour of the under surface in this species is peculiar ; the prosternum is 

 testaceous with its process black, the breast is black with a large dash of yellow 

 on the front part of the hind coxa?, while the ventral segments are yellowish, 

 marked with black especially at the sides and apex : the yellow lateral band of the 

 elytra is broad, and is divided at the apex by a large space into two parts, the 

 anterior of which is quite distinct. I have not seen enough specimens to know 

 whether there is much variation in the species. 



The species has undoubtedly much in common with D. latissimus, particularly 

 the labrum, the nature of the punctuation, the form of the yellow band at the apex 

 of the elytra, and the condition of the clothing of the male tarsi ; it departs, however, 

 widely therefrom by the undilated margins of the wing-cases, the form of the coxal 

 processes, and the unsulcate elytra in the female. In certain respects it resembles 

 D. verticalis, and although the two at present are widely separated I should not 

 be surprised if intermediate species are found to exist in North America. 



Noi-th Amei-iea, (Pennsylvania, Kansas, Lake Superior, Vancouver's Land, sec. Crotch). 9.53. 



III. 4.— Tribe HYDATICIDES. 



Posterior tarsi with the hind margins of their joints densely fringed with 

 adpressed and flattened cilire or squamsB overlapping the basal portion of the 

 following joint. 



7i^ T? F^ T 1*^ ^ 

 Prothorax, with a tine lateral margin, ....... ,„. 



° ' (Vide IX 699.) 



Prothorax without lateral margin, episternal suture curvilinear, spurs of ) Thermonectini. 



hind tarsi emargiuate at apex. j {Vide p. G7 '2.) 



Prothorax without lateral margin, episternal suture rectilinear, spurs of] Hydaticini. 



hind tai-si accuminate at apex. j ( Vide below.) 



II. 13. — Group Hydaticini. 



Metathoracic episternum large, the suture between it and the wing of the 

 metasternum rectilinear, spurs of posterior tibia? quite acuminate. 



Claws of posterior feet nearly equal, i ^fj9-^^'^i^F^'- 



'■ I (Vide p. 648.) 



Claws ofposterior feet very unequal | ^rl^/'^^aR^s 



^ ( {Vide p. 648.) 



