602 Mr. Blackwall's Descriptions of new Species of Spiders. 



family Dysderidœ, to which it unquestionably appertains, and of placing it, 

 together with Segestria perjida and Segesfria senoculuta, both species of con- 

 siderable dimensions and provided witii four branchial sacs, among- the spi- 

 ders of the second division, or those which have only two sacs*. 



Having endeavoured succinctly to point out the insufficiency of the charac- 

 ters selected to distinguish the foregoing primary groups into which spiders 

 have been divided, I venture to recommend the difference in tiie number of 

 eyes with which those animals are provided as the most satisfactory basis of 

 their distribution into tribes ; supplying, as it does, well-defined characters 

 not difficult to be ascertained, and being in perfect harmony with the leading 

 principle on which the subordinate groups are, for the most part, esta- 

 blished. 



In the present limited state of our knowledge of the order Araneidea it 

 admits of a division into three tribes only. 



1. OcTONocuLiNA. Eyes eight. 



2. Senoculina. Eyes six. 



3. BiNocuLiNA. Eyes two. 



The first tribe, Octonoculina, is much the most extensive of the three, com- 

 prising numerous genera, which present considerable differences in organiza- 

 tion and œconomy : closely connected with this group by intimate relations 

 of affinity and analogy, the second tribe, SenocuUua, includes seven or eight 

 genera, species belonging to most of which are indigenous to Great Britain ; 

 and the third tribe, Binoculina, contains the single genus Naps, which has 

 been recently established by Mr. MacLeay for the reception of two remark- 

 able species of extra-European spidersf. 



The newly-discovered spiders described in the following pages are arranged 

 according to the method proposed above; and it is a fact deserving of notice, 

 that they have been captured, without exception, in the north of England and 

 Wales. 



Considering the narrow limits within which my researches in ai'achnology 



* Cours d'Entomologie, p. 514-15. 



t Annals of Natural History, vol. ii. p. 2, et seq. 



