250 
[October 
the outer side with an attenuated margin (or flange) which is narrow to i their 
length and then expands slowly and gradually as far as i their length, when 
it is suddenly contracted to ^ its width, so as to form an angular tooth, and 
tapers out at J their length. Viewed laterally the superiors taper rapidly on 
their basal J and afterwards very slowly; and they curve downwards, their 
lower edge describing a circular arc of 45° for 4-5ths their entire length, then 
suddenly become straight and taper to a very fine, long, acute point. At the 
change in the curvature there is an elongate inferior tubercle, truncate for its 
whole length in a direction parallel with the straight terminal portion of the 
appendage, and about l-7th or l-8th as long as the appendage itself. The in¬ 
feriors are | as long as the superiors, as wide apart at base as they are and 
more divaricate, obliquely but almost vertically flatfish, rapidly tapered when 
viewed flatways, very slowly tapered when viewed edgeways, their inside sur¬ 
face a little excavated, their outer surface a little rounded, straight for f their 
length, when they curve inwards and upwards in a quadrant and terminate in 
a robust cone with a very minute thorn at tip directed upwards. Legs black ; 
anterior femora with a ‘^posterior” pale green vitta. Wings hyaline, scarcely 
flavescent at base; veins black, the costal vein greenish yellow in front to the 
pterostigma; pterostigma dark brown, surmounting 3^—4 cells; membranules 
moderate, whitish. Antecubitals 11; postcubitals 10. Two discoidal areolets, 
commencing with 3 in both wings. 
Length % 48 mill. Expanse % 57 mill. Abd. % 34^ mill. Sup. wing % 30^ 
mill. Inf. wing 29.^ mill. Pterost. inf. 3 mill. Post, femur % 8 mill. Ap¬ 
pend. sup. li mill. Width of 8th ventral 3} mill. 
One % ; 9 unknown. In measuring the width of the 8th ventral in 
Gromphus care should be taken not to include the spiracle-bearing 
membrane which connects what may be called the “ sternum’’ or cen¬ 
tral piece of the venter with the attenuated margin or “ pleura” of the 
dorsum. In Odonata the abdominal spiracles are situated in this mem¬ 
brane, generally close to the “ sternum,” and are generally very small 
and not easily seen except by inflating the abdomen) which individual 
Gromphus sometimes do of their own free will in the interval between 
their capture and their death. The subfamily Gromphina, which has the 
tip of abd. % more or less dilated, is remarkable for the spiracle of the 
8th ventral being larger than the others and very conspicuous. Just so 
Dytiscus in Coleoptera, who has a habit of sticking his anus out of the 
water to draw his breath, has his anal spiracle much larger than the 
others. In vastus and ventricosus and probably in the other two spe¬ 
cies belonging to this group, this spiracle on the 8th ventral is situated 
rather further from the ventral “sternum” than in other Gomphus. 
Ventricosus is readily distinguishable from all allied Gromphus but 
dilatatus, externus and vastus by the terminal abdominal joints being 
