CHAP. XV CLASSIFICATION 385 
308 species, divided among six families. Blackwall’s beautiful 
work, the Spiders of Great Britain and Ireland, was published 
by the Ray Society in 1864. He divides spiders into three 
tribes, Octonoculina, Senoculina, and Binoculina, according to the 
number of the eyes, and describes 304 British species, distributed 
among eleven families. 
His successor in this country has been Pickard-Cambridge, 
whose work, under the modest title of Zhe Spiders of Dorset 
(1879-81), is indispensable to British collectors. 
Blackwall’s division of the order into tribes was evidently 
artificial, and has not been followed by later Arachnologists. 
Dufour (1820) founded two sub-orders, Dipneumones and Tetra- 
pneumones, based on the presence of two or four pulmonary sacs. 
Latreille (1825) established, and many Arachnologists adopted, a 
division into tribes based upon habits, Orbitelariae, Retitelariae, 
Citigradae, Latigradae, etc., and this method of classification was 
followed in the important work of Menge, entitled Preussische 
Spinnen, which was published between 1866 and 1874. 
Since 1870 determined efforts have been made to grapple 
with the difficult subject of Spider classification, notably by 
Thorell and Simon. The latter, undoubtedly the foremost living 
Arachnologist, writes with especial authority, and it is inevitable 
that he should be largely followed by students of Arachnology, 
who cannot pretend to anything like the same width of outlook. 
It is indicative of the transition stage through which the 
subject is passing that Simon in his two most important works,’ 
propounds somewhat different schemes of classification, while in 
the Histoire naturelle, where his latest views are to be found, 
he introduces in the course of the work quite considerable 
modifications of the scheme set forth in the first volume. 
In that work the order is divided into two sub-orders, 
ARANEAE THERAPHOSAE and ARANEAE VERALE, the first sub-order 
containing Liphistius and the Mygalidae or Theraphosidae of 
other authors, while all other spiders fall under the second sub- 
order. The Araneae verae are subdivided into CRIBELLATAE and 
ECRIBELLATAE, according to the presence or absence of “cribellum” 
and “calamistrum” (see p. 326) in the female. Important as 
these organs doubtless are, the Cribellatae do not appear to form 
1 Arachnides de France (vol. i., published 1874). Histoire naturelle des araignées 
(2nd ed. vol i., published 1892). 
VOL. IV 2C 
