182 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
MONOPS Lubbock. 
Fourth aud fifth thoracic segments fused; head without lateral hooks; no dorsal or- rostral eye- 
lenses; ventral eye rather flatly convex to club-shaped; rostral filaments delicate, long and flaccid; 
fifth thoracic segment with pointed lateral corners, usually asymmetrical in male; abdomen of female 
with 1 or 2 joints, asymmetrical in both male aud female. Anterior antennae of female 16-jointed, 
in the right antenna of male joints 13 and 14, 16 aud 17, 19 to 21, and 22 to 25 fused. Mandibular blade 
with blunt teeth. Second basal joint of maxilla scarcely half 
as long as second internal lobe; third internal lobe present. 
Posterior maxilliped 5-jointed. Inner ramus of first pair of 
feet 3-jointed. 
Female: Cephalothorax 5-jointed. Anterior antenna short, 
16-jointed, joints 2 to 5, 6 to 8, 9 to 11, 13 and 14, and 24 and 25 
fused ; appendages similar to those of Pontella, though reduced 
in number and length. In posterior antennae the distal basal 
joint is fused with proximal joint of inner ramus ; outer ramus 
short and slender. Mandibular blade scarcely dilated toward 
tip, usually with short, blunt teeth. In maxilla the second 
inner marginal lobe is more than twice as long as second basal 
joint, which is fused with the two joints of inner ramus. Dis- 
tal uncinate bristles of anterior maxillipeds long in compari- 
son with proximal ones, sparsely provided with prickly plumes. 
Proximal basal joint of posterior maxillipeds broad, lobular, 
followed by only 4 further joints. Feet similar to those of 
Pontella. 
Male: Sexual differences in structure of trunk, anterior 
antennae, and fifth pair of feet. Anterior portion of cephalo- 
thorax asymmetrical, and usually the right projection of last 
thoracic segment is longer than left and of a peculiar form. 
Abdomen with 5 segments; genital opening sinistral ; third 
segment with an outgrowth on right side. Left anterior 
antenna differing from that of female, especially in separation 
of thirteenth and fourteenth joints; proximal joints of right 
anterior antenna incrassated, middle joints dilated, disciform. 
Besides joints 2 to 5, 6 to 9, 10 to 12, 13 to 14, 19 to 21, and 22 
to 25, joints 16 and 17 are also fused. Fifth pair of feet on 
the whole similar to that of Pontella. 
19. Monops regalis Dana. 
Last thoracic segment pointed on either side, in the male 
prolonged on right side into a powerful slightly curved hook. 
Abdomen of female with 2 segments, asymmetrical with out- 
growths. Furca short. In male the proximal hook in forceps 
of right fifth foot is somewhat longer than distal hook. 
Coloration: Dark blue-green, and similar to that of Pontella and Anomalocera. 
Length of female, 4 to 4.4 mm; male, 3.4 to 3.5 mm. 
A single male specimen of this species was taken in Gulf Stream tows, 70 miles south of Marthas 
Vineyard, July 25, 1899. 
ACAKTIA Dana. 
Fifth thoracic segment and abdomen of male symmetrical; the latter with abbreviated anal seg- 
ment. Anterior antennae of female 17-jointed, throughout of nearly uniform thickness, with knob-like 
projections at insertions of the long, usually plumose but sometimes spinose bristles; grasping 
anteuna of male with but slightly incrassated middle joints. Outer ramus of posterior antennae 
much shorter than inner ramus; second joint of inner ramus elongated, first joint with 9 bristles on 
its inner border. Mandible with rather elongate second basal joint; rami incompletely joiuted; outer 
ramus articulating about on middle of margin of second basal. First outer lobe of maxilla with long 
bristles; outer ramus rudimental, represented by 2 bristles. Proximal lobes of anterior maxillipeds 
19. Monops regalis Dana; male; a, dorsal as- 
pect; b, right anterior antenna; c, fifth pair 
of feet. 
