286 
arachnides. 
attention to tlie respiratory organs of Spiders, and it is from him that 
we have taken ovir divisions, whicli consist of tliose 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 Theraphosae of Walckenaer, and some 
other genera of the one he collectively designates by the name of 
Spiders, accoi’ding 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 chelicerae 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 ai’e : 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, Avith the internal angle of the superior exti'emity 
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 chelicerce 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 mammilla;, those which, 
in the Spiders of the ensuing division, are placed between the four exterior ones, and 
are, there, very visible ; as they are here but scarcely apparent, I have not thought it 
requisite to notice them. 
