On EUROPEAN SPIDERS. oul 
metrical webs; and as a calamistrum is found in spiders, whose industry is 
so different, it appears to us that its importance in the construction of the 
web cannot always be particularly great. 
The 12 families adopted by BLACKWALL all constitute natural groups, 
with the exception of the CenZlonide, of which we have already spoken, 
and in some degree the Vheridiide, which family in DLACKWALL comprises 
only the Walckenaerian genera Theridium and Pholcus; for the remaining 
genera Of SUNDEVALLS Theridides he has formed the family Zinyphüde. 
This division of the old family Theridides is certainly unnecessary: BLACK- 
WALL does not mention a single character of the animals themselves, whereby 
the families may be distinguished. Pholcus appears to us rather to belong 
to the Scytodoide, and that family should immediately follow the Theridio- 
ide. — The families are very briefly, often insufficiently or not at all, 
characterized: the genera also very briefly, but in general with sufficient 
detail for practical behoof in the examination of an unknown form. 
BLACKWALL, as regards the number and extent of the genera he 
adopts, is much more conservative than WESTRING; he acknowledges but 
a small number of new generie groups over and above those already 
established by WALCKENAER, like whom, in determining the limits of the 
genera, he appears to fix his attention almost exclusively on the characte- 
risties of the organs of the mouth, the position of the eyes, and the rela- 
tive length of the legs. The greatest part of the genera proposed by others, 
for ex., C. KocH, and the distinctions of which are founded also on charac- 
teristics deduced from other parts of the body, are rejected by BLACKWALL, 
although they, if often in a more or less modified form, appear to have 
been pretty generally acknowledged by the arachnologists of the Continent. 
The authors remarks on the instincts, haunts and general economy 
of the species described, their manner of constructing their webs ete., are 
particularly valuable and interesting. The descriptions of the species are 
themselves, with few exceptions, very fully detailed, and, in combination 
with the figures, sufficient for the recognition of the species. Especial 
attention has been very properly paid to the form of the palpi of the males, to 
the construction of the spinners and other finer details of structure, except 
as regards the spines wherewith the legs and palpi are armed, which are 
only superficially touched upon. The descriptions are however often occu- 
pied in a great measure by charaeters, which, as common for the whole 
genus or most of the species comprised by it, are of little or no use in 
determining the species. We wish to call attention to this as an impedi- 
ment in the use of the work, as also, and that especially, to the absence of 
