On Aquatic Carnivorous Coleoptera or Dytiscide. 705 
The species* are all South American and may be arranged in six groups as 
follows. 
{Size moderate, about 30 m.m. long; a vague yellow 
lateral band on wing-cases ; termination of meta- + Group 1. (Nos, 1103 and 1104). 
sternal wing far from epipleura. 
Size small (about 22 m.m.); no yellow lateral band ; 
apex of metasternal wing near to epipleura; ¢ inner Group 2. (No. 1105.) 
claw shorter and finer than outer one. . 
= 4 Size small (about 23 m.m.); inner claw on hind foot of } 
males as large as the other ; apex of metasternal wing | 
near to epipleura; with or without lateral yellow } Group 3. (Nos. 1106 to 1109). 
band on elytra; females with a beautiful sexual | 
sculpture. J 
Size moderate (29 m.m.); elytra with yellow stripe; apex 
of metasternal wing near to epipleura; female Group 4. (No. 1110). 
| without sexual sculpture. f 
ber, of equal or nearly equal lengths ; 
in female one long claw with a more 
side; the smaller spur of hind tibia 
rudimentary one on its under and inner 
simply acuminate at apex. 
Claws on’ hind feet of male two in num- 
smaller spur of hind tibia minutely tridentate or trituber- 
culate at the apex. 
Group 5. (Nos. 1111 to 1116.) 
Two claws of about equal length on hind tarsus in each sex ; smaller 
spur of hind tibia largely bifurcate at extremity. 
Each sex with two claws of nearly equal length on hind foot; | 
\ Group 6. (Nos. 1117 and 1118). 
Grovp 1. 
1103. Megadytes expositus, n. sp.—Ovalis, elongatus, sat convexus, nitidus, supra 
olivaceus, vage testaceo-cinctus, subtus piceus, pectore prosternoque in mediis 
olivaceo-metallescentibus ; pedibus quatuor anterioribus rufis, posterioribus piceis 
trochanteribus dilutioribus ; pectore longitudinaliter arcuato ; femoribus posteriori- 
bus angulo externo spinoso-acuto. Long. 32, lat. 163 m.m. 
The male has the front tarsi small attaiming only 2 to 23 m.m. in the transverse 
direction ; the intermediate tarsi have long sexual hairs on the two basal joints, and 
a slight tendency to a similar development on the third joint. ‘The females have 
a very fine and obsolete sexual sculpture on the wing cases, consisting of very fine 
punctuation and some very short indistinct scratches along the middle towards the 
base. 
* Reference should also be made to Cybister eeneus, Orm. (No. 1274 huj. op.)? No. 1104 var.; South 
America. 
