34 NEW YORK STATE MUSEUM 



somewhat quadrangular labrum covered above with stout bristles 

 and fringed beyond the bristles around its border with copious 

 soft yellowish hairs (pi. 6, fig.2). Labium with two jointed palpi of 

 singular form, the basal joint of each cylindric, naked; the second 

 joint twice as long, flattened, its inner margin straight, its outer 

 margin arcuate, its exterior border closely beset with a single 

 linear series of long thin setae, its apex bearing a minute obtuse 

 inwardly directed prominence, set off by a minute notch from 

 the inner margin, and perhaps representing the remains of a 

 palpal segment (pl.6, fig.3). Galea and lacinia hairy beneath, 

 the latter less than half as large as the former and more 

 triangular in outline. Mandible naked (pl.6, fig.4), the outer 

 canine tridentate at tip, the inner one spine-like, but with a flat 

 margin on one side below overlapping the palp. Maxilla (pl.6, 

 fig.5) with palpus two-jointed and similar in form to the labial 

 palpus; end of lacinia terminating in a long straight spine; a 

 copious tuft of gill filaments takes origin under the base of the 

 stipes. 



Thorax strongly arched dorsally arid slightly flattened laterally. 

 Legs short and stout, the tibia longest in the fore leg, where 

 one third longer than the femur, decreasing in length successively 

 on middle and hind legs. Fore legs with a remarkable develop- 

 ment of stiff fringes of tawny hairs, a single ventral fringe on 

 the femur, a double fringe beneath the tibia, the basal portion 

 containing hairs as long as the combined tibia and tarsus, ibut 

 the length of the fringe diminishing apically, and a nruch shorter 

 single fringe beneath the tarsus. There is also on the fore leg a 

 single elongate and flattened tibial spvr, more than half as long 

 as the tarsus, and strongly recalling by its form and structure 

 the flat spur on ' the swimming legs of the diving beetle 

 Cybister (pl.6, fig.7). The single tarsal claw is short and 

 arcuate and denticulate on its inferior margin; on middle and 

 hind tarsi the claw acquires a special convexity on the basal part 

 of its inferior denticulate surface, especially marked in the hind 

 tarsus (pl.6, fig.9). There is a large tuft of several times forked 

 gill filaments attached to the base of the fore coxa within. 



Abdomen cylindric at base, becoming depressed and upcurved 

 posteriorly and laterally carinate, the lateral margins on seg- 

 ments 8 and 9 ending in long, straight, sharp lateral spines, half 

 as long as their respective segments. There are minute and in- 

 conspicuous lateral spines also on segments 1 to 7, hardly more 

 than acute angles on 1-4. Gills on segments 1-7, covered by obo- 

 vate protecting lamellae (Plate 6, fig.10), which are slightly 

 oblique, increase slightly in size on segments 1-3 and are 

 equal on 4-7. Each lamella has the front margin, the 



