KEY TO GUATEMALAN SPECIES OF ZILCHIA PRETZMANN, 1968

1. G1 with apex oblong; field of apical spines well developed, open (not concealed by apical margins); cephalic surface distinctly curved towards cephalic side distally, cephalic lobe absent ................................................ 2

— G1 with apex narrow, slit-like; field of apical spines poorly developed, nearly concealed by apical margins; cephalic surface of distal portion nearly straight distally, with well-developed spiny cephalic lobe (Fig. 10A, B ... .......................................................................................................................... Z. germani Pretzmann, 1978

2. G1 with mesial process bearing upper margin serrate; cephalic process as conical spine approximately as large as the mesial process; apex with mesocaudal margin entirely bordered by row of teeth (Fig. 11 F-I) ................ ............................................................................................................................................ Z. coronata n. sp.

— G1 with mesial process bearing upper margin smooth; cephalic process as short conical spine distinctly smaller than mesial process; apex with mesocaudal margin unarmed (Fig. 10C, D)..................................................... .............................................................................................................. Z. falcata Rodríguez & Hobbs, 1989