Key to the species of the nasutus group

1 Lateral dark bands along the body, nuchal collar absent, blackish head and belly........................... P. nigrilatus

- Nuchal collar present, lateral dark bands absent, head not as above............................................... 2

2 Dorsal coloration brown with dark sides.......................................................... P. lativittatus

- Dorsal coloration homogeneous red.......................................................................3

3 Ventral scales <210 in females and <194 in males; dorsal coloration pale red, supralabials with few dark blotches...................................................................................................... P. nasutus

- Ventral scales> 215 in females and> 195 in males; dorsal coloration brilliant red, labials plates variable in color.......... 4

4 Labials plates unblemished...................................................................... P. concolor

- Supralabials, sometimes infralabials and gullar region, black blotched.............................. P. labiomaculatus .