Ewing — New North American Acarina. 67 
GAMASUS Latreille. 
Peritreme present, more than twice as long as broad; leg I with 
claws; dorsal shield large, entire; male with genital opening on the 
anterior margin of sternal plate; leg II of male frequently enlarged and 
armed with large chitinous horns or tubercles; sternal plate of female 
scarcely reaching the hind coxe; genital plate of female triangular, 
being angulate anteriorly. 
Three species. 
KEY TO SPECIES. 
1. Second pair of legs of male not swollen 2. 
Second pair of legs of male enormously swollen G. magnicornutus. 
_ 2. Second pair of legs of male provided with a sharp tooth on the inner 
side of each femur G. oblongus. 
Second pair of legs of male possessing a large horn G. unicornutus. 
Gamasus oblongus Nn, Sp. 
Da! OR GE LM 
Pale brownish grey; body darker than the appendages. 
Palpi three-fifths as long as the anterior pair of legs; distal segment 
equal in length to the penultimate but not so stout; penultimate segment 
with a sharp spine at its inner distal aspect; antepenultimate segment 
poth longer and stouter than the penultimate segment and bearing two 
small spines on its inner side; second segment, the stoutest of all and 
with one small spine on its inner side; mandibles stouter than the palpi 
and when extended may surpass the same, chele as long as the two 
distal segments of the palpus and uniformly toothed on their inner 
margins. The mandibles are jointed toward their middle. Cusps of 
the hypostoma sharp, slightly curved and about one-half as long as the 
chele of the mandibles. 
Body broadly rounded behind and subtruncate in front, slightly com- 
pressed just above the second pair of legs. Dorsal surface of the body 
sparsely clothed with clavate bristles, including a prominent straight 
' shoulder pair and a curved pair situated on the posterior margin. 
Anterior pair of legs slightly longer than the body; tarsus one and 
a half times as long as the tibia; tibia and antepenultimate segment 
subequal. Claws of the anterior pair of legs smaller than the others and 
situated on very slender pedicels. Second pair of legs stouter than the 
rest; hind pair of legs as long as the anterior pair and with long slender 
tarsi. All the legs are provided with rather stout bristles. 
Length, 0.50 mm.; breadth, 0.30 mm. 
In moss. Collected by L. M. Smith, at Marion, III. 
Gamasus unicornutus N. sp. 
Pl. X. f. 26-27. 
Light yellowish brown; chele of the mandibles darker brown than the 
rest of the body. 
