32 T. THORELL, 
diagnoses, a want which is felt as much the more, as the author seldom se- 
parately gives any hints as to the characters by which the species most 
resembling each other may best be distinguished. The unit of length for 
expressing the dimensions of the animals is also, as it seems to us, not 
very well chosen. Instead of stating, as most zoologists do, the size of 
such small animals in millimeters or lines and decimals of one or other of 
these units, DLACKWALL measures the length and breadth of the spider's 
cephalothorax, abdomen etc. by fractions of an inch difficult to compare, 
so that one is sometimes obliged to submit the given measure to an arith- 
metical reduction, before it is possible to form a clear idea of the relative 
size of the parts described. — The figures are, with a few exceptions, 
(as e. g. some in Pl. I and IT) good. Not only are coloured entire figures 
of both the male and female of almost every species given, but also outli- 
nes of the male’s palpi, frequently also of the position of the eyes, the diffe- 
rent organs of the mouth, and so forth. The large and difficult genera 
Neriene and Walckenaera (= Erigone WESTR.) are treated with especial 
care, and indeed there scarcely exists in arachnological literature anything 
surpassing the superb, highly magnified figures, that BLACKWALL has 
furnished of these remarkable little spiders. 
BLACKWALL in his synonyms cites but few arachnological works; 
excepting his countryman LISTER he mentions none of the older authors, 
non even CLERCK or FABRICIUS: he generally follows, and only with a too 
implicit confidence, the determinations and nomenclature of WALCKENAER. 
Accordingly, as we shall hereafter see, his specific names will be frequently 
obliged to give place to other, older denominations. In other respects he 
appears in his nomenclature to have conscientiously observed the law 
of priority. 
9. "Histoire Naturelle des Araignées (Araneides) par Eugène Simon” 
is a work differing in many respects from the two preceeding, and which 
we here submit to examination only on account of the "Catalogue synony- 
mique des espèces européennes” appended to it. The work contains a descrip- 
tion of the internal and external structure of spiders, followed by a detailed 
account of their division into families, sub-families and genera, a list of 
the species belonging to each separate genus, as also an account of the 
principal species’ haunts and economy. The plan and object of the work 
are clearly set forth by the author in the following words: "résumer . . . 
dans un cadre restreint tous les travaux anciens et modernes qui ont été 
publiés sur cette classe d'animaux, en y joignant les observations qui me 
sont propres, tel est le but que je me suis proposé en publiant ce traité." 
