286 ARACHNIDES. 



attention to the respiratory organs of Sjnders, and it is from liim that 

 we have taken our divisions, which consist of those that have four 

 pulmonary sacs — with as many external stigmata, two on each side, 

 and closely approximated — and of such as have but two*. The first, 

 which embraces the order of the Theraphosse of Walckenaer, and some 

 other genera of the one he collectively designates by the name of 

 Spiders, according to our method form but the single genus 



Mygale. 



Their eyes always situated at the anterior extremity of the thorax, 

 and usually, closely approximated ; feet and cheliceree robust ; copu- 

 lating organs of the males always salient and frequently very simple. 

 Most of them have but four fusi, of which the two lateral or external, 

 situated somewhat above the others, are longest, and consist of three 

 segments, exclusive of the prominence that forms their peduncle. 

 They weave silken tubes in which they reside, and which they con- 

 ceal either in holes excavated by them for that purpose, or under 

 stones, bark of trees, or between leaves. 



The Theraphosse of Walckenaer will form a first division, the 

 characters of which are: 1. Four fusif, of which the two that are 

 intermediate and inferior are usually very short, and the two that are 

 exterior very salient; the hooks of the chelae doubled underneath, 

 or along their carina or inferior edge, and not on the inner 

 side of their internal face, or upon it; eight eyes always, usually 

 grouped on a little eminence, three on each side, forming a reversed 

 triangle, and the two superior ones approximated ; the remaining 

 two arranged transversely between the preceeding 



The fourth pair of legs are the longest, and then the first ; the 

 third is the shortest. 



Here the palpi are inserted into the superior extremity of the jaws ; 

 so that they appear to consist of six joints, the first of which, narrow 

 and elongated, with the internal angle of the superior extremity 

 salient, fulfils the functions of a jaw. The ligula is always small and 

 nearly square. The last joint of the palpi of the males is short, has 

 the form of a button, and bears the organs of generation at its extre- 

 mity. The two anterior legs of the same sex have a stout spine or 

 spur at their inferior extremity. Such are the characters of the 



Mygale, Walck., 



Or the true Mygales. In some of them we find no transverse series 

 of horny and moveable spines or points, resembling the teeth of a rake, 

 at the superior extremity of their chelicerae immediately above the 

 insertion of the claw or hook which terminates them. The hairs 

 which decorate the under part of their tarsi form a thick and broad 



* Section of the Territelse of our first edition. 



f I have perceived, in the Atypi, vestiges of two other mammillae, those which, 

 in the Spiders of the ensuing division, are placed between the four exterior ones, and 

 are.tliere, very visible ; as they are here but scarcely apparent, I have not thought it 

 requisite to notice them. 



