Hydraena hintoni, new species Figs. 15 (aedeagus), 18 (habitus), 151 (spermatheca), 194 (map) Type Material. Holotype (male): Brazil: Matto Grosso, Porto Velho, 31 viii – 1 ix 1937, H. E. Hinton. Deposited in the BMNH. Paratypes: Same data as holotype (3 BMNH). Differential Diagnosis. Similar in dorsal habitus to H. takutu and H. curvosa (Figs. 16–18); differentiated from H. curvosa by the differently shaped anterior part of the pronotum and the smaller size (ca. 1.58 mm vs. 1.76 mm); differentiated from H. takutu by the differently shaped posterior part of the pronotum and larger size (ca. 1.58 mm vs. 1.48 mm). The male metatibiae have large setal brushes, the shapes and placements of which are unique among American Hydraena. The aedeagus of H. hintoni shows some basic plan similarities with the aedeagi of the compared species, but markedly differs in many details (Figs. 15, 19–20). Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.58/0.68; head 0.30/0.35; pronotum 0.35/0.45, PA 0.39, PB 0.38; elytra 0.92/0.68. Dorsum of head with frons dark brown to piceous, clypeus brown; pronotum brown except disc dark brown, diffusely margined; elytra and legs brown to dark brown; maxillary palpi testaceous, tip not darker. Frons punctures ca. 2–5xef, much larger and denser near eyes than medially; interstices microreticulate laterally, narrow walls to 1xpd, shining, 2–4xpd medially. Clypeus microreticulate laterally, very finely sparsely punctate medially. Mentum and postmentum finely, moderately densely, punctulate, shining. Genae raised, shining, posterolaterally with shallow transverse sulcus delimiting ill-defined posterior ridge. Pronotum subcordiform, sides weakly sinuate in front of arcuate middle, more markedly sinuate behind middle, turning outward basally, posterior angles acute; anterior margin straight behind eyes, rather markedly emarginate behind frons, scintilla absent; punctures on disc much larger and deeper than those of frons, interstices shining, 0.5–3xpd, punctures larger and denser at anterior and posterior; PF1 very shallow, obsolete; PF2 absent; PF3 deep, PF4 moderately deep, shallowly confluent; no low ridge between PF3 and lateral margin. Elytra appearing humped, very convex at summit of posterior declivity, at about midlength; lateral explanate margins wide; on basal 1/3 punctures ca. 1xpd largest pronotal punctures, punctures becoming finer and much more widely spaced toward posterior. Intervals not raised, shining, on basal 1/3 ca. 1–2xpd, as are interstices between punctures of a row, a few punctures subserial. Apices in dorsal aspect conjointly rounded, in posterior aspect margins forming very shallow angle with one another. Ratios of P2 width and plaque shape (P2/w/l/s) ca. 4/1/7/8. P1 not laminate, width ca. 3/4 P2; median carina sinuate in profile. P2 l/w ca. 3/2, sides slightly converging toward blunt apex, apex raised to same level as median carina of mesoventral intercoxal process. Plaques narrow, carinate, very slightly arcuate, widely separated, slightly converging toward one another anteriorly, located at sides of deep median depression. Metaventrite with anteromedian carina and with longitudinal ridge on each side, extended posteriorly from margin of each mesocoxal cavity. AIS width at straight posterior margin ca. 2x P2. Protibia slender, straight, medial margin in distal 1/2 slightly emarginate and with row of short setae. Mesotibia straight. Metatibia markedly widened in distal 1/2 and bearing two large brushes of setae, one on medial margin and one on dorsolateral margin. Male abdominal apex symmetrical; last tergite without apicomedian notch. Female (microslide mount, n=1): last tergite broadly rounded, without apicomedian notch, ca. 20 well hooked, moderately long setae, separated into two groups by small median gap; gonocoxite divided by weakly sclerotized midlongitudinal area, apical margin broadly rounded, lacking transverse ridge; spermatheca disc type (Fig. 151). Etymology. Named in honor of the collector, the perceptive and prodigiously productive Howard E. Hinton. Distribution. Currently known only from the type locality (Fig. 194).

Published as part of Perkins, Philip D., 2011, New records and description of fifty-four new species of aquatic beetles in the genus Hydraena Kugelann from South America (Coleoptera: Hydraenidae), pp. 1-198 in Zootaxa 3074 on pages 21-22, DOI: 10.5281/zenodo.1050060