82 M. A. Vayssiére on the 
Compound Eyes and Ocelli (fig. 12).—The compound eyes 
show astrongly marked black tint ; they are inserted upon the 
outer, lateral margins of the head, nearly at the intersection of 
these margins with its base. ‘They are hemispherical. On the 
dorsal surface of each of them, a little behind the middle, we 
observe a groove, which does not surround it completely. 
This peculiarity places these organs of, vision in the section of 
ascalaphoid compound eyes of certain Ephemerina (Lepto- 
phlebia). The facets of these organs are not always hexagonal ; 
they often present only four or five sides; or their outlines 
may even be irregular. 
The ocell’, with their very convex cornea, are easy to dis- 
tinguish even by the naked eye, owing to their whitish colour. 
The lateral ocelli are placed within and a little in front of 
the compound eyes; the median ocellus, as already stated, 
occupies the middle of the space between the antenne, and is 
almost in the anterior margin of the head. 
Legs.—The organs of locomotion are all atrophied in the 
perfect insect ; this modification, which is observed in a great 
many other adult Ephemerina, must be in relation to the short 
duration of the life of the animal in this state ; it is therefore 
very probable that, after copulation (and oviposition in the 
case of a female), Prosopistoma punctifrons speedily dies. 
We hope that future investigations will soon enable us to fll 
up this gap. 
The legs are very unequal: the shortest are those of the 
first pair, and the longest belong to the third pair (fig. 14). 
The colour of these organs is very light brown, depending some- 
what upon the thinness of the chitinous envelope, the surface of 
which also is but little clothed with hairs. The first two joints, 
coxa and trochanter, are pretty well formed in all the legs, and 
are even strongly developed in those of the first pair; the form 
of the femur ot the anterior limbs is not much modified, whilst 
it is more or less modified and atrophied in the other legs. 
The last three portions, tbia, tarsus, and claw, are always 
deformed, and often actually twisted into a corkscrew, in all the 
legs. 
“In the figure of the insect seen from the ventral surface I 
have represented (fig. 8) only the first two joints of the first 
pair; in fig. 14 I have given a representation of one of the 
legs of the third pair under a power of about 50 diameters. 
In this last pair the general atrophy is more marked even than 
in the two ‘others. 
Wings.—The organs of flight are greatly developed in 
Prosopistoma, which is not surprising, considering the atrophy 
of the legs, and the necessity under which the insect in con- 
