844 On Aquatic Carnivorous Coleoptera or DytiscidcB. 



I. 1 G. —Genus A MPHIZOA . ( Vide p. 318.) 



Tliree closely allied species form this aggregate. The}^ are insects of somewhat 

 elongate, moderately convex form, the outline much interrupted at the junction of 

 the thorax and elytra ; the colour is an uniform dull black, and the surface is 

 sculptured with a coarse, indefinite, but close punctuation. 



The head is rather broad and short ; when in position in the thorax its breadth 

 is about one-fourth greater than its length from the front of the thorax to the front 

 of the clypeus, and when extracted the bi-eadth is still a little greater than the 

 length : the eyes are rather small in proportion to the size of the head, they are 

 slightly convex and prominent, and occupy chiefly a lateral position, their encroach- 

 ment on the area of the upper and undersurfaces being but small. The clypeus is 

 separated from the posterior part of the head by a fine suture, distinct across the 

 whole width of the head, the clypeus has about twice the area of the exposed 

 portion of the labrum, and is quite continuous with the plane of that part ; the 

 anterior angle of the clypeus is not folded under in front of the antennal cavity. On 

 the under surface the transverse sutures on the lateral portions of the head are very 

 difficult to trace. The mentum is united with the base of the head by a very fine 

 nearly obliterated suture, and is extremely large, and extends forwai'ds quite as far as 

 the front of the labrum, the mandibles and maxilliB being completely covered by its 

 large lateral wings ; the outer lobe of the maxilla is curved and palpiform, but is 

 not divided by any articulation. 



The antennse are short and stout, and of simple construction, their basal joints 

 are punctate or porous ; this punctuation becomes more indistinct on the terminal 

 joints so that the outer ones are nearly smooth and shining ; there is no pubescence 

 to be seen on any of the joints. 



The prothorax has the pronotum flat, the sides coarsely and irregularly crenulate 

 so that it would be incorrect to say that there either is or is not a lateral margin. 

 The prosternum is rather large, the length of the band in front of the coxa being 

 equal to that of the coxal cavity, along the middle in the longitudinal direction it is 

 flat, and shows no trace of any thickening along the middle, it is prolonged back- 

 wards between the rather widely separated coxse, so as to form a flat, short, broad, 

 prosternal process, the extremity of which is truncate-rounded : the side pieces are 

 large, the suture between the anterior and posterior of them is in some inchviduals 

 difficult to detect, but when seen it is found that the posterior piece is of large area, 

 probably more than half that of the anterior piece. The coxae are suborbicular and 

 rather small. 



The mesosternum is rather small, and its plane of extension is almost a continua- 

 tion of that of the metasternum, so that in the natural condition the mesosternum 

 is quite visible between the meta- and pro-sterna, its epimera are triangular : thus 

 the general form and relative size and disposition of its parts are singularly similar 



