Key to the species in the genus Deltorhinum (slightly modified from Génier 2010)

1. Anterior pronotal portion modified mediallyı either lobate or bilobate along anterior edge and depressedı anterior portion of the hypomeron deeply excavated. Deltorhinum ............................................................................................................................................... 2

- Anterior pronotal portion unmodifiedı or if modified then anterior portion of the hypomeron very feebly excavated .. some Ateuchus Weber species that can be confounded with Deltorhinum ı including A. genieri ........................................................... n. n.

2. Pronotal anteromedial portion unilobate...................................................................................... 3 - Pronotal anteromedial portion bilobate (pronotal sulcus bearing two lobes).............. 6

3. Anterior pronotal portion lacking small median transverse bulge on depressed portion.......................................................................................................................................................... 4

- Anterior pronotal portion with a small median transverse bulge on depressed portion; Brazil (Xingu-Araguaia interfluve in southern Pará) .. Deltorhinum vazdemelloi Génier 4. Pygidial basal thirdı presenting fine coarse punctures; Brazil (Upper Amazon and Rondônia) ................................................ .............................................. Deltorhinum batesi Harold.

- Basal portion of pygidium rugoseı apical portion finely punctate .................................. 5

5. Head frontal carina arcuate median portion feebly lower than the lateral portions. Medial sulcus distinct on the posterior thirdı fainted at the anterior edge. Paramera curved and widely separated apicallyı curved inner borders; Brazil (Lower Amazon)... ................................................................................................................... Deltorhinum genieri nov. sp.

- Head frontal carina straight in dorsal viewı median portion as high as in the sides. Pronotal longitudinal sulcus complete joining the posterior and anterior portions. Paramera curved and closely separated apicallyı straight inner borders; French Guiana ............................................................................................. Deltorhinum guyanensis Génier

6. Pronotal longitudinal sulcus wideı edges extending obliquely outward anteriorly... 7

- Pronotal longitudinal sulcus narrow. Edges not extending obliquely outward ante- riorly; Brazil (Mato Grossoı Mato Grosso do Sul).. ........ Deltorhinum bilobatum Génier.

7. Anterior portion proceed a round gibbosity towards front; Bolivia ....................................... ................................................................................................... Deltorhinum kempffmercadoi Génier

- Anterior portion bilobate proceed a v-shaped gibbosity towards front; Brazil (Mato Grosso)................................................. ............................................... Deltorhinum armatum Génier