12 THE IMMATURE STATE OF THE ODONATA. 
long, narrow, middle third of front border somewhat produced in two triangu- 
lar lobes, rather deeply cleft; on each side of cleft highly developed spinous 
processes. Legs very slender. Processes enclosing right angle; posterior 
longer, anterior thicker. Abdomen long; lateral spmes on segments six to 
nine. Appendages sharp, middle one as long as the inferiors, not deeply 
notched ; laterals somewhat shorter, male projection conical. 
1. GYNACANTHA? SPECIES. 
PuateE III. Fre. 2. 
Hagen, Stettin Zeit. XIV. p. 268. 
Locality unknown, probably Brazil. Nymphz two, male and female not 
fully grown, types described by Hagen. Length, 42 mm.; breadth, 7 mm. 
oO 
~ 
: 
A smaller nympha from Charleston, $. C., and one from Florida, and some 25 
mm. length from Rio San Francisco, Brazil, Thayer Exp., are identical. 
Body exceptionally slender and elongated, flat. Head very flat, and 
longer than broad. Eyes elongated, two thirds the length of head, narrow, 
moderately prominent, at the hind inner angles somewhat produced ; sepa- 
rated from occiput by straight Ime. Ocelli hardly discernible, space between 
the eyes in general shape almost square. The two parts of the vertex are 
not very distinctly marked. The lobe at the sides large and polished ; part 
behind the eyes one third the length of head; sides straight; occiput long 
and deeply notched ; hind angles acute, and with polished bands separated 
by roughened lines on upper side. Antenne very slender, little longer than 
head, exceptional in having the sixth joint longest. Mask extending to be- 
tween hind legs, very long and narrow, enlarged abruptly at apical third 
to twice the width of basal portion; middle third of front border deeply 
cleft, into two very prominent teeth, placed one on each side on the inner 
slope of the cleft. Palpus finely denticulated, cut nearly straight at tip ; 
hooks of palpus prolonged so as to more than meet ; movable hooks extending 
beyond the base of each other, cylindrical. Prothorax nearly as broad as back 
part of head, rounded behind. Processes enclosing right angle, posterior 
one longer, anterior thicker. Legs slender, hind legs reaching middle of 
seventh segment. Thorax small; wing cases in the largest specimen, extend- 
ing only a little beyond first segment. Abdomen long, slender, small at base 
and enlarged as far as seventh segment; thence tapering, smooth; the eight 
impressions not very distinct. The four middle ones, transverse ; dorsal band 
