26 
Psyche 
[Vol. 90 
Wolff 491. This specimen consists of head, thorax, and the basal 
area of two wings, but nothing can be made of the venation. The 
prothorax is large and bears at least seven spine bases. The head is 
preserved at a slight angle to the prothorax. Labrum is visible, as are 
one antenna and both eyes. 
MCZ 222. Reverse half. Costal margin of the fore wings and most 
of the hind wings preserved. This insect is small for the species (hind 
wing measures 45 mm long, 14 mm wide) but the venation is indis- 
tinguishable from that of the holotype. 
Gerarus collaris 
Figures 12 and 13 
Gerarus collaris Handlirsch 1911:314, 1919:30. 
Gerarus longicollis Handlirsch 1911:315, 1919:30. new synonymy. 
Description 
Fore wing: length 45-50 mm, width not known. Venation of fore 
wing obscured in all specimens. 
Hind wing: length 40-45 mm, width 10-12 mm; RS apparently 
five-branched, M deeply forked; CUA and CUP parallel. 
Prothorax: small, 1 1 mm in length and narrow (approximately 6 
mm wide). Posterior, or bulbous region, 7-8 mm long. Broken 
spines are present on all G. collaris specimens examined, but no 
more than six can be seen on any one specimen. 
Diagnosis 
This is the smallest of the Gerarus species. Unfortunately, the 
venation in all known specimens is not clear enough to serve as a 
species level character. G. collaris is, therefore, best recognized by 
its prothorax, which tapers gradually from the anterior to the poste- 
rior end, and is much narrower and shorter than in other species of 
Gerarus. The distinctive nature of the prothorax, and its usefulness 
as a species-specific character, can be seen by comparing figs. 5, 1 1 
and 13. 
Geological range: Westphalian D. Occurrence: Mazon Creek, 
Illinois, U.S.A. 
Holotype: Gerarus collaris YPM 34. Specimen examined. 
Obverse half. Fore and hind wings overlap in this specimen, only the 
costal margin of the fore wing is well preserved. The prothorax is 
intact and several spine bases are visible, but the overall preserva- 
tion is mediocre. 
