62 CONTENTS OF EACH VOLUME. 
at hand being insufficient for the purpose. They are said to date back at least as 
far as the Carboniferous period, when they were represented by forms of which the 
two species of Liphistius are the sole survivors. The earliest known Arachno- 
morphid spiders in any way resembling those living belong to the Oligocene times. 
At that period there existed many forms, very similar to those occurring at the present 
time, whose remains have been found in amber washed up on the shores of the Baltic 
Sea. The Opiliones are stated to have preceded, during the Carboniferous epoch, the 
air-breathing scorpion, Anthrascorpius, and their specialization probably began during 
the still earlier Silurian times, since in that period there existed an Arachnid which 
is a true scorpion in every sense, except that it had apparently no trace of air-breathing 
lung sacs. The ‘ Harvestmen’ make no web for the ensnaring of their prey, and the 
females, after depositing their eggs, take no further interest in their offspring. In the 
two volumes 1181 species are enumerated, this number including the 422 described 
as new in Vol. II. ‘The Opiliones number 70 species, 58 of which are described as 
new, with 11 new genera. The ninety-three plates (39 in Vol. I. and 64 in Vol. II.) 
include figures of 981 species. 
12. ARACHNIDA ScorPIONES, PEeprpatri, and Souiruc#: by R. I. Pocock. 
Very little material was available for the study of these Arachnids, sixty-nine species 
only being enumerated for the three groups. The twelve uncoloured plates include 
figures of thirty-seven species. The Scorpiones are represented by three families, the 
Pedipalpi by two, and the Solifuge by a single family. 
In this Volume the author gives the geographical distribution under the heading 
for each genus, and no general ‘ Introduction’ to the whole subject was prepared, for 
want of data. 
13, ARACHNIDA ACARIDEA: by O. Stoll. 
‘The material for this subject was obtained almost entirely by the author during a 
residence of nearly five years in Guatemala. He made the drawings on the spot, but 
unfortunately he had no modern literature on Acarids with him, and his microscope 
was anything but satisfactory. Dr. Stoll’s work, therefore, must be treated as a 
contribution to the fauna of Guatemala, rather than as an enumeration of the 
Acaridea inhabiting Central America. The types of the species described remained 
in his possession. In his ‘Introduction’ (published in 1893), p. vii, he states that it 
is remarkable that not one of the forms described represents a generic type entirely 
new or peculiar to the region. Doubtless a great deal remains to be done in the 
way of collecting before we shall have any true idea of the Acarid-fauna of Central 
America. 
The twenty-one coloured plates illustrate 43 species. 
