396 
CLASS ARACHNIDA. 
are always projecting, and often very simple ; the majority 
have but four spinnerets, two of which, lateral or exterior, and 
situated a little above the other two, are longer, with three 
articulations, not reckoning the elevation formed by their 
peduncle. They fabricate silken tubes, which serve them for 
an habitation, and which they conceal, either in burrows that 
they have excavated, or under stones, the bark of trees, or 
between leaves. 
The theraphosae of M. Walckenaer will form a first 
division, having for characters — four spinnerets, the two in- 
termediate and inferior very short, and the two exterior 
extremely projecting ; crooks of the forceps bent under- 
neath along their keel or lower edge, and not within or on 
their internal face; eight eyes in all, most frequently grouped 
on a small eminence, three on each side, forming, when 
united, a reversed triangle, and the upper two approximate, 
the other two disposed transversely, at the middle of the 
preceding. 
The fourth pair of feet, and after them, the first, are the 
longest ; the third is the shortest. 
In some the palpi are inserted at the upper extremity of 
the jaws, so that they appear to be composed of six articula- 
tions, of which the first, narrow ai|d elongated, with the in- 
ternal angle of the superior extremity projecting, performs the 
office of jaw. The tongue is always small, and almost square; 
the last articulation of the palpi in the males is short, in the 
form of a button, and bearing at its extremity the sexual 
organs. The two anterior legs of the same individuals have 
a strong spine, or spur, at their lower extremity. Such are 
the characters of 
Mygale (proper), Walck. 
Some do not present at the upper extremity of their forceps 
immediately above the insertion of the claw, or hook, which 
