ArT. 21. DRAGONFLIES OF BURMA AND LOWER SIAM—LAIDLAW. 93 
as unlikely.) Another species bayadera resembles this small group 
in being without a T-shaped mark on the frons, and in having brown 
legs. But it differs markedly in having the abdominal base much 
less distended, the auricles relatively much smaller, and the third ab- 
dominal segment much less narrowly constricted. The lower anal 
appendage is nearly half the length of the upper pair which are about 
5 mm.long. The species is a small one with the hinder wing of the 
male about 37 mm. long; the wings are relatively broader than are 
those of the three last species. It has apparently a much wider range 
than those species and is recorded from the Himalayas, India, Burma, 
the Malay Peninsula, and islands as far as the Celebes. 
GYNACANTHA HYALINA de Selys and SUBINTERRUPTA Rambur. 
The two species hyalina and subinterrupta are evidently very closely 
allied; both have a well-defined T-shaped mark on the frons. The 
base of the abdomen is more inflated, and the auricles relatively larger 
than in bayadera, but not to the same extent as in basiguttata and 
still less than in dohrni and in its immediate allies. The upper anal 
appendages of the males are about 6 mm. long, shaped like a single- 
edged straight sword, more than twice as long as the lower append- 
ages in the case of hyalina, three times as long or a trifle more in 
subinterrupta. Both are species of moderate size, the hinder wing 
having a length of about 43 mm. and the abdomen of 46 mm. Ris 
gives the following as among the chief characters separating hyalina 
from subinterrupta. Pterostigma distinctly and invariably shorter 
(3 mm. as against 3.5mm). The T-shaped mark of the frons broader 
both in the longitudinal and in the transverse part. The coloring is 
also different, hyalina according to Ris is brilliant blue and green in 
the adult, subinterrupta with a nuance of brown only; hyalina has the 
knees dark brown, swbinterrupta has the legs entirely light brown. 
Both species have a wide distribution. Ris gives for hyalina 
Formosa and the Philippines, for subinterrupta Celebes, Java, and 
Lombok. The United States National Museum has two specimens 
of hyalina from lower Siam, and I have examined specimens (females 
only) in the Indian Museum labeled hyalina by de Selys, himself, 
from Assam. 
GYNACANTHA HYALINA de Selys. 
Two males, Trong, Lower Siam, Dr. W. L. Abbott, collector; col- 
lection of the U.S.N.M. 
One specimen immature, both faded to a dark dull brown. The 
anal appendages resemble almost exactly those figured for the species 
by Ris, and are exactly like those of an Indian specimen before me. 
Length of abdomen 43 mm., of hinder wing 43 mm., of upper anal 
appendages 6.5 mm., of pterostigma 3 mm. 
