1863.] 
251 
very widely distended, joint 8 expanding mill, in consequence of 
the unusual width of the terminal ventrals. From dilatatus it is at 
once separated by the much larger size of that species, the total length 
of which is 72 mill, and that of the superior wing 41 mill., and also 
by the face of dilatatus being fasciate with black.—From externus it 
differs as follows:—Is^. The stripes of the thoracic dorsum are deep 
black, as in vastus, not “ brown.” 2nd. The humeral and antehume- 
ral are confluent nearly throughout; in externus they are not conflu¬ 
ent at all. 3/y7. The posterior pleural stripe is absent and the anterior 
one abbreviated above, nearly as in fraternus; in externus both stripes 
are present and unabbreviated. Abdominal joints 8—10 are dor- 
sally immaculate; in externus they are distinctly vittate with greenish 
yellow, bth. The earlets are widely tipped with black as in vastus; 
in externus they are immaculate with fine black teeth, ^th. The pos¬ 
terior femur is only i of the total length of the body; in externus it 
is nearly 1.—Finally, although at first sight it would easily be con¬ 
founded with vastus, it differs from that species as follows :—Is^. The 
size is smaller, the smallest specimen of 6 S vastus now before me be¬ 
ing 521 mill, long, sup. wing 321 mill. Out of eleven 'S vastus measured 
by me in 1862, the length only varied from 53—55 mill., and three 9 the 
same. 2nd. The face is immaculate; in vastus the face (if we include 
the labrum) is trifasciate with black, ^rd. It has one long yellow 
spot behind the eye; vastus has two small ones which are never con¬ 
fluent. 4:th. The median thoracic stripe is rather narrow, its sides are 
parallel and it is obliquely truncate at tip, the obtuse angle outwards; 
in vastus (11 'S 9 specimens) the median thoracic stripe is wider, dis¬ 
tinctly obcuneiform, and obliquely truncate at tip, the acute angle out¬ 
wards, except in a single % where it is squarely truncate and scarcely 
obcuneiform. bth. The humeral and antehumeral are confluent for a 
long space ; in vastus never at all. Qtli. It has only one pleural stripe, 
and that abbreviated on its upper half; vastus has two, never abbre¬ 
viated, though the anterior one is sometimes interrupted for a short 
space. Ith. The dorsal vitta of abdominal joints 3—6 is scarcely ab¬ 
breviated at tip; in vastus it is greatly abbreviated. 8^A. In vastus 
there is a small inferior thorn near the tip of the superior abdominal 
appendage % ; in ventricosus this thorn becomes a long truncate tu¬ 
bercle. \n ventricosus there is a distinct lateral flange on the outside 
