578 Wisconsin Academy </f Sciences, Arts and Letters. 
plainly wider behind than in front, occupying 3-5 of the cephalo¬ 
thorax. Front middle eyes subtouching, about twice as large 
as laterals and separated from them, these four forming a 
straight or slightly curved row. Second row plainly nearer first 
than third. Third row as wide as cephalothorax. Coxae I sep¬ 
arated by width of labium, which is not much, if at all, longer 
than wide. Sternum narrowed in front, and truncated. Coxae 
and trochanters I elongated in the males, except in nervosus. 
This distinct genus is represented in the United States by 
four species, rufipes, Bettini, sexpunctatus and nervosus. Iri- 
descens B., which Mr. Banks has kindly lent us for examina¬ 
tion, is founded upon an example which is not quite mature, and 
we think it may be Bettini. The males have obliquely directed 
falces, with long fangs, and two apophyses, one strong and ver¬ 
tical, coming down from the inner proximal end of each falx, 
and a heavier, hammer-headed one on the outer side. 
There is so much Variation in color, size and marking within 
the limits of each species, as to make it difficult to distinguish 
them by these points. Fortunately the palpi and epigynes are 
distinct. 
KEY TO ZYGOBALLUS-MALES. 
r Face and sides of cephalothorax beyond second row of eyes, 
| covered thickly with white scales. Tib. I about 4 
| times as long as wide. 
Sides of cephalothorax dark, or covered with rather in¬ 
conspicuous whitish scales. Tib. I either 5-6, or only 
2 1-2 times as long as wide. 
f Cephalothorax with a large white spot at the beginning of 
the thoracic slope. Bulb of palpus with a longitudinal 
2 <{ division . sexpunctatus 
| Cephalothorax with no white spot on thorax. Bulb of 
l palpus with a transverse division. Bettini 
f Patella and tibia I long and slender, tibia 5-6 times as long 
| as wide. Found only in Texas and farther south.... rufipes 
Joints of first leg comparatively short. Tibia 2 1-2 times 
as long as wide. Found in New England and as far 
l south as Virginia. nervosus 
The females of Zygoballus must be distinguished by the epi- 
:gynes, of which we give illustrations. 
