62 
pair of flattened ones behind the eyes. Antenne with the 
basal joint globular, the second smaller; third joint very flat, 
nearly circular, but with the inner edge straight. Below the 
eye a blunt process extends downward and forward to the sides 
of the labium, obviously for lateral support of that organ. 
Labium short and thick; mentum slightly wider than 
long, contracted at basal fourth; median lobe of mentum occu- 
pying hardly a third of its width, slightly rounded, its thick- 
ened edge obscurely cut into about ten blunt teeth, and bear- 
ing a fringe of flat scales, with a few more elongate and 
bristle-like at the ends of the fringe; lateral lobes arcuate, 
broad and strong, with ill-defined blunt denticulation all around 
the rounded tip and down the inside; movable hook short, 
feebly arcuate, tapering, with an incurved tip. 
Prothoracic dorsum elevated at sides into prominent com- 
pressed lateral ridges, between which it is excavated. Femora 
inclined to be sharp-edged posteriorly and triangular in cross- 
section. 
Abdomen with dorsal hooks beginning on 2, at first narrow 
and acute, highest on 3, becoming gradually more elongate 
and blunt, variably reduced on the last three or more segments 
to low median ridges; lateral spines of 2 acute, those of 3-9 
appearing as broad triangular projections of the latero-posterior 
angle, those of 9 inclosing segment 10. Appendages short and 
thick, triangular-pyramidal, longer than the very short 10th 
segment. Superior slightly shorter than the inferiors, laterals 
one third as long. Longitudinal ventral impressions of abdo- 
men separated by only about one fifth of the width of the 
abdomen, nearly parallel, becoming strongly divergent on 2 
and 9. Young nymphs have the peculiarities of the mature 
ones even more strongly marked, especially in the form of the 
abdomen, which is more nearly circular. 
VI. Lantruus Needh. 
The nymph of the single eastern species for which this 
genus was established, differs from the ordinary Gomphus nymph 
