1985] 
Wilson — Cretaceous and Eocene amber ants 
211 
ants, however, by its more convex promesonotum and more numer- 
ous and less evenly distributed mandibular teeth (4 in all Erebo- 
myrma and 5 in the Old World species of the closely related genus 
Oligomyrmex). 
Iridomyrmex mapesi, new species 
(Figs. 4, 5) 
Diagnosis {worker). An Eocene species tentatively assigned to 
Iridomyrmex on the basis of the overall habitus, antennal form, and 
structure of the mandibles, which fall within the limits of the living 
and fossil species placed within that genus. The preservation of the 
single type is not good enough to make a detailed comparison with 
all of the previously recognized forms of Iridomyrmex, but the fol- 
lowing minimal characterization is possible. The worker of mapesi 
is larger and possesses fewer mandibular teeth than the living New 
World species and /. hispaniolae and /. humiloides of the Miocene 
Dominican amber. In these traits mapesi falls within the range of 
some of the contemporary members of the Indo-Australian calvus, 
cordatus, and rufoniger groups. Hence, in a purely technical sense it 
is not possible to separate mapesi from all other known ants, but on 
the combined basis of its age, geographical location, and morphol- 
ogy this form can be safely treated as a distinct species. 
Holotype worker. Head Width 1.06 mm, Head Length 1.1 mm 
(measurable only to the nearest 0.1 mm), Eye Length 0.11 mm, 
Pronotal Width 0.62 mm. Other visible details as illustrated in Figs. 
4 and 5. Deposited in the Museum of Comparative Zoology. 
The species is named in honor of Royal H. Mapes, the discoverer 
of the Arkansas amber, who also collected the type specimen. 
/. mapesi is the oldest verifiable record of the subfamily Doli- 
choderinae. The following note may be of additional, ecological 
significance: a small segment of leafy liverwort (Hepaticae) is 
embedded close to the head of the I. mapesi worker. According to 
Alice F. and Rolla M. Tryon, who kindly identified the fragment, 
the presence of these plants indicates a mesic habitat, presumably 
either swampland or mesic forest. 
Protrechina, new genus 
Diagnosis {worker). A small Eocene formicine close to Para- 
trechina in habitus, differing from that genus in its lack of a circlet 
