HACKBERRY PSYLLIDS. 
617 
Monothalamous galls — Continued. 
Gall smaller, semi-globular, sessile, covered with long soft hair and 
without impression P. c.-pubescens n. sp. 
Gall smaller, globular, subsessile, with a small impression at top, 
not pubescent P. c- globulus n. sp. 
Gall smaller, not pubescent, sessile, wider than high, very much flat- 
tened on top, and here usually with two concentric elevated rims, 
and provided with a central nipple P. c-.cucurbitau. sp. 
Gall smaller, not pubescent, less sessile than the preceding, higher 
than wide, around the sides near top with longitudinal sulci, the 
top cup-like, depressed, and without central nipple. 
P. c.-curcurbita var.? 
The following characteristics of the galls are condensed from more 
elaborate descriptions, which I hope to publish in a more complete 
paper on the biology of the North American Psyllidse. 
36. P. venusta Osten Sacken (Stett. Eut. Zeit., 1861, p. 422).— Gen- 
erally globular, but often more or less irregularly ovoid, or even elong- 
ate. Color varying from pale buff to brown ; surface opaque, with scat- 
tered, small, flattened postules. Diameter of globular form varying 
from 7 to 20 mm , The gall consists of an outer shell and an inner core, 
which can easily be separated upon cutting the gall open. The outer 
Fig. 201.— Gall of Pachypsylla venusta: a, gall fully 
formed; &, same forming; c, same in section, natuial size. 
After Riley. 
shell is very hard and woody, varying in thickness from 1 to "3 m ™. The 
apical portion of the gall has on one side a slit which is deepest and 
widest at the tip and connects here with the funnel-like, twisted, basal 
portion of the leaf. This slit exposes to view the inner core, which con- 
sists of the very thin and brittle walls of the irregular cells which fill 
