1983] 
Burnham — Geraridae 
43 
Fig. 25. Nacekomia russae, photograph of fore wing of holotype no. FMNH PE 
791 . Length 43 mm. 
Diagnosis 
Although the prothorax is unknown, venation of fore and hind 
wings is typical for the family. I have retained this as a distinct genus 
only on the basis of the diminutive size of its one species, and this 
may change as more material is found. 
Geological range: Westphalian D. Occurrence: Mazon Creek, 
Illinois, U.S.A. Type species: Gerarulus radialis. 
Gerarulus radialis 
Figures 26 and 27 
Gerarulus radialis Handlirsch 1911:316, 1919:30. 
Description 
Fore wing: length 25 mm as preserved (estimated as 35 mm), 
width 1 1 mm; SC parallel to C, terminating on it; R simple, RS 
branched (at least two or three times); M anastomosing briefly with 
RS, appearing to be four-branched; CUA simple, CUP elbowed 
towards CUA; two anal veins visible, each forking once. 
Hind wing: length 21 mm as preserved (estimated as 30 mm), 
width 10 mm; SC and R simple and parallel to C; RS pectinate, 
although the number of branches is unknown; CUA and CUP inde- 
pendent from one another and parallel; anal area slightly enlarged; 
abdomen, although indistinctly preserved, appears to be rather 
slender; prothorax missing. 
