SUBORDER MALLOPHAGA. 249 
hairs, pallettes small, beneath with a central elevated ridge; posterior edge above 
sinuous, distinctly concave each side of occiput, lateral angles produced; prothorax 
widening a little behind, posterior margin concave. 
Legs rather long, hind ones reaching nearly to end of abdomen; abdomen of usual 
form for genus, sides slightly arcuate but nearly parallel, of the same color as head 
and thorax. A very narrow brown line parallel] to sides of thorax and abdomen 
(in line of spiracles). 
Described from three specimens from the ruby-throated humming 
bird ( Trochilus colubris Linn.) in Cornell University collection, kindly 
loaned by Prof. J. H. Comstock. 
It is quite different from any other species of the genus known to me 
in the uniform color. 
-Gyropus ovalis Nitzsch. 
Gyropus ovalis Nitzsch, Germar’s Mag., Vol. III, p. 304; Burmeister, Handbuch, Vol. I, p. 443; 
Denny, p. 245, Pl. XXIV, fig. 1; Giebel, Epiz.; Piaget, p. 609, Pl. L, fig. 5; Osborn, Bull. 7, 
Div. Ent., Dept. Agr. 
Specimens received from Dr. A. Hassall, of Baltimore. Evidently 
a common parasite of the Guinea pig, its only host. 
Gyropus gracilis Nitzsch. 
Pediculu. porcelli Schrank, Ins. Aust., p. 500, Pl. I, fig. 1. 
Gyropus gracilis Nitzsch, Germar’s Mag., Vol. III, p. 304; Burmeister, Vol. II, p. 443; Denny, 
p- 246, Pl. XXIV, fig. 2; Piaget, p. 611, Pl. L, fig. 6; Osborn, Bull. 7, Div. Ent., Dept. Agr. 
Common, along with preceding, upon the Guinea pig. Numerous 
specimens collected by Dr. Hassall, Baltimore, Md. 
