1941] 
Antiquity of Social Insects 
53 
for the projections are remarkably uniform in shape and 
height, c) The cells of Vespid nests tend to radiate from the 
base of the nest, the individual cells being distinctly wider 
at their openings than at their bases. In the fossil the “cells” 
have a constant width for their entire length and there is no 
indication of a radiating arrangement, d) the walls in the 
cells of a wasp nest are of paper thickness only ; in the fossil 
the substance between the “cells” is nearly as thick as half 
the diameter of the “cells”. 
These discrepancies between the fossil and the structure 
of known Recent Vespid nests, in addition to the difficulty 
of accounting for preservation of such a fragile structure, 
lead us to reject Dr. Brown’s conclusions regarding this 
specimen. We believe the interpretation of Celliforma 
farosites is altogether too uncertain and problematical for 
it to be accepted as a Cretaceous wasp nest without more 
proof than has been offered and in view of the total absence 
of remains of fossil Vespidae, either social or solitary, from 
that period. 
We might point out that there is some superficial resem- 
blance between Dr. Brown’s fossil and certain “fossil nests” 
which have been recently described from Uruguay by 
F. Lucas Roselli , 4 and which are thought to be of Cretaceous 
age, also. We refer particularly to the fossil named Uruguay 
auroranormai, which shows a somewhat similar arangement 
of cells of even diameter from top to bottom, ending in dome- 
shaped bases; the cells are not represented by casts, how- 
ever, but are hollow, with their own walls preserved. If 
such structures were filled with sand or mud, they might 
presumably after hardening become “fossils” similar to that 
described by Dr. Brown. Some of the Uruguayan nests are 
claimed by Roselli to be the work of solitary diplopterous 
wasps, although this seems to us extremely problematical. 
Without examining these nests and knowing more about the 
conditions under which they occur, we cannot of course 
discuss them further; but they look suspiciously like nests 
built by certain Recent solitary bees. The female of the 
European Halictus quadricinctus , for example, digs a spa- 
cious chamber at the end of a tunnel in the soil, in which she 
4 Boletin de la Sociedad Amigos de las Ciencias Naturales 
Kraglievich-Fontana”, vol. I, pt. 2, September 1938, pp. 72-102. 
