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 Eay 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 The 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, Dipueumones 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, Eetitelariae, 

 Citio-radae, Latisradae, 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 difticult sul;)ject of Spider classification, notably by 

 Thorell and Simon. The latter, undoubtedly the foreniost 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 natiirelle, 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 verae, the first sub-order 

 containing Liphistius and the Mygalidae or Theraphosidae of 

 other authors, Nvhile 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 " calamistnmi " (seep. 326) in the female. Important as 

 these organs doubtless are, the Cribellatae do not appear to form 



1 A rachnides dc France (vol. i., published 1874). Histoire naturelle des araignecs 

 (2nd ed. vol i., published 1892). 



VOL. IV 2 c 



