710 On Aquatic Carnivorous Coleoptera or Dytiscide. 
punctuation near the sides, aud there are also a few fine punctures scattered over its 
surface ; the internal claw of the hind feet remains rudimentary and can only be 
seen at the base and underside of the larger claw. 
The only two specimens I have seen of this species, I obtained from Castlenau’s 
collection ; one of them which is rather larger and broader than the other, was 
standing side by side with a male of another species, labelled ‘‘ Cybister fallax, Aube, 
dubius Lucz. Cayenn.” ; the other was standing alone labelled “‘ Cybister puncticollis, 
Brullé, Bo. Ayres,’ while on the pin was a label, “ Bresil, Col. Dejean.”” Iam not 
at all sure that this is really Brulldé’s C. puncticollis which was found on the River 
San Miguel, centre of Bolivia. 
South America, (? Buenos Ayres; ?Cayenne). 1106. 
Group 5. 
1111. Cybister fallax, Aubé, 7rogus fallax, M.C.—Ovalis, parum latus, convexus, 
nitidus, supra olivaceo-niger, capite anterius prothoraceque ad latera testaceis, 
elytris vitta intramarginali posterius lata sed parum arguta, testacea ; subtus niger 
pedibus quatuor anterioribus rufis, pedibus posterioribus picescentibus ; elytrorum 
epipleuris parum latis. Long. 27, lat. 15} m.m. 
I have not seen any male of this speeies, the female has no trace of any sexual 
sculpture. _ 
The species is readily distinguished from others of this group, by its smaller size 
and narrower form ; the yellow band on the elytra is broad, at the shoulder it 
quite touches the lateral margin, after that is distinctly separated from it, behind 
the anterior two-thirds of its length it becomes broader and again reaches the 
margin, though in a s)mewhat vague manner, just before the extremity it is dilated 
by joining an agglomeration of small ferruginous dots, and terminates as a point at 
the suture. 
I have seen only two individuals of this species, one of them, from Dejean’s 
collection, was there labelled “ Trochalus fallax mihi, h. in Cayenne, D. Lacordaire” : 
the other was in Edwin Brown’s collection and labelled in his handwriting “ Cybis- 
ter flavocinctus, Chev., Mexico.” The determination being wrong it is probable 
that the locality also of this latter specimen may be erroneous. 
Cayenne ; !Mexico. 1107. 
1112. Megadytes obesus, n. sp.—Ovalis, latus, parum elongatus, convexus, supra 
olivaceo-niger, capite anterius prothoraceque lateribus testaceis, elytris vitta intra- 
marginali ante apicem evanescente testacea; subtus niger, pedibus quatuor 
