16 (15). 
5 (10), 
the classification of British Crabronidae, 387 
Sixth joint distinctly emarginate beneath 
Xestocrabro, Ashm. (= Solenius, Auct.). 
Front femora becoming suddenly widened from the base, 
So as to be subangulate beneath near the base; clypeus 
produced in the middle at the apex; 3rd antennal joint 
LATO ae ae, eR a microstictus, H. Schf. (= larvatus). 
. Front femora gently rounded beneath from the base ; 
clypeus broadly rounded apically in the middle; 3rd 
antennal joint longer, twice ag long as wide or more. 
X. vagus, L. 
Sixth antennal joint not emarginate beneath, all the joints 
simple, 
Tooth on inner edge of mandibles rather small; clypeus 
apically in the middle bluntly pointed; basal joint of 
middle tarsi simple. M etacrabro, Ashm., M. lituratus, 
Panz. 
Tooth on inner edge of mandibles very large; clypeus 
apically in the middle broadly rounded or almost truncate ; 
basal joint of middle tarsi subangulately dilated, 
M. (2) quadricinctus, F. (¢nterruptus, Saund.) an. gen. nov. ? 
CRABRONINAR. 
9. 
» Superorbital foveae sharply defined; basal abdominal 
segment strongly punctured (mandibles 3-dentate at 
apex and with a tooth on the inner edge), 
Thyreus, Lep., T. clypeatus, Schr. 
- Superorbital foveae absent or ill-defined or very feeble ; 
basal abdominal Segment at most very finely and feebly 
punctured. 
- Mandibles 3-dentate at apex and without a distinct tooth 
on the inner margin towards the middle, at most with 
the margin faintly sinuate or with a trace of an angulation, 
Antennae with the third joint very elongate, becoming in 
Some aspects conspicuously slender behind the apical 
portion, fully twice as long as the fourth; clypeus apically 
in the middle strongly produced and on each side of the 
produced part there is a strong emargination, forming on 
each side a prominent tooth; ocelli generally in a sub- 
equilateral triangle (more obtuse-angled in chrysostomus), 
Clytochrysus, Mor, 
Ocelli in a nearly equilateral triangle; size larger, 
