176 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
14 . Metridia hibernica Brady & Robertson. 
Female: Cephalotliorax about If times as long as abdomen; lateral corners of fifth thoracic seg- 
ment slightly pointed; genital segment somewhat shorter than fourth and fifth abdominal segments 
together, and fifth abdominal only three-fourths as long as fourth ; furca somewhat shorter than 
fifth abdominal segment and twice as long as broad. Anterior antennae scarcely reaching posterior 
margin of genital segment, 
joints 2 a, b, c, and 3 to 11 
each with 2 gesthetasks. 
Terminal bristle of third 
joint of outer ramus of 
fourth foot but little more 
than one-fourth as long as 
joint. Fifth foot 3-jointed 
with 3 long bristles on ter- 
minal joint. 
Male : Grasping an- 
tenna on right side. Fifth 
foot has second joint of outer 
ramus of left foot without, 
first joint of outer ramus of 
right foot with, a long 
thorn; the latter and the 
third joint of right outer 
ramus relatively shorter 
than in M. longa Lubbock. 
Length of female, 2.45 
to 2.85 mm. ; of male, 2 mm. 
This species was very 
common in the tow taken by 
the Fish Hawk in Plymouth 
Harbor iu August, 1899. A 
single female specimen was 
found in tow taken at Woods Hole, December 15, 1898. 
tinctively a boreal species. 
14. Metridia hibernica Brady & Robertson; a, male, dorsal aspect ; 6, female, dorsal 
aspect; c, female, proximal joints of right anterior antenna; d, female, second foot; e, 
female, fifth pair of feet; /, male, fifth pair of feet. 
Like Temora longicornis, M. hibernica is dis- 
PLEUROMMA Claus. 
A dark, pigmented, chitinous knob on side of first thoracic segment. Furca at most twice as 
long as broad. Anterior antennae 23-jointed; joints 1 and 2 ab fused (2c separate), 7 to 9 fused, 24 
and 25 separate. Rami of first to fourth pairs of feet 3-jointed; first joint of outer ramus of third 
pair with deep incision on the outer margin; terminal bristle of third pair short, bent over to outside; 
first joint of inner ramus of second pair with hooks on inner margins, in female on both sides, in 
male only on one side; fifth pair of feet in female rudimental, 2 to 4 jointed; in male 5-joiuted on 
either side, without true forceps. Grasping antenna of male sinistral or dextral. 
Female: Cephalotliorax with 5 segments, the last two thoracic segments fused; rostral filaments 
plumose, inserted on a papilla; pigmented chitinous knob of first thoracic segment on left or right 
side. Abdomen with 3 segments, symmetrical. Anterior antennae toothed along anterior margin of 
proximal joints; joints 1, 3, 7, 14, 18, 21, 24 with elongated distal bristle; a?sthetasks short, filiform. 
Outer ramus of posterior antenme longer than inner, 7-jointed. Mandibles and maxilke similar to 
those of Calanus and Centro pages; anterior maxilliped with strongly projecting fifth lobe; posterior 
maxilliped with elongated inner ramus. The first four pairs of feet with 3-jointed rami ; first basal 
joint with well-developed inner bristle on all, second basal joint with inner bristle on first pair. 
Bristles of rami : Outer ramus with 1, 1, 2 outer bristles, 1, 1, 4 inner bristles in first, with 1, 1, 3 
outer bristles, 1, 1, 5 inner bristles in second pairs; inner ramus with 0, 0, 1 outer bristles, 1, 2, 4 
inner bristles on first, 0, 0, 2 outer and 0, 2, 6 inner bristles on second, 0, 0, 2 outer and 1, 2, 6 inner 
bristles on third, and with 0, 0, 2 outer and 1, 2, 5 inner bristles on fourth pairs, 
Male: Sexual peculiarities in structure of trunk, anterior antenme, fifth and other pairs of feet. 
Abdomen with 5 segments, sometimes asymmetrical, with dextral or sinistral genital orifice. 
