1.   The adoral shields are slightly wing-like, not or just separating the oral shield from the first lateral arm plate.

2.   The adoral shields are small wing-like almost separating the oral shield from the first lateral arm plate.

3.   The oral shield is a large, rounded arrow shape.

4.   The oral shield is basically rhombic but in some specimens the distal lobe is produced and the plate becomes arrow shaped.

5.   The oral shield is oblong to rhombic.

6.   The oral shield is quite large and arrow shaped.

7.   The oral shield is rhombic but often with an obtuse proximal angle and a convex distal edge.

8.   The oral shields is a rounded pentagonal with an obtuse or slightly rounded proximal angle.