168 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Female: Head distinct from tliorax; rostral threads delicate; abdomen short, with 3 segments; 
genital segment and furca symmetrical; anterior antennas of asymmetrical length, more than twice 
as long as the body, 23-jointed, with a few very long bristles; inner ramus of posterior antennae 
nearly twice as long as outer ramus; the succeeding appendages similar to those of Calanus; feet 
short; outer rami 3-jointed, inner ramus of first pair 1-joiuted, of second to fourth pairs 3-jointed; 
filth pair of feet with 2-jointed basals and 3-joiuted outer rami, without inner rami. 
5. Mecynocera clausii J. C. Thompson. 
The only species of this genus; very transparent, colorless, or with a few red spots. In excep- 
tional cases the bristles of furca and of anterior antennte are red. Length, 0.92 to 1 mm. A single 
specimen was taken in the Gulf Stream July 25, 1899; the male is unknown. Thompson took the 
species near the Canary Islands and at Malta. Giesbrecht gives the following localities: Naples; 
Pacific Ocean, to 138° W., between 3° S. and 15° N., from surface to a depth of 1,000 meters. 
PARACALANUS Bceck. 
Second basal joint of first pair of feet with an inner marginal bristle; proximal portion of outer 
margin of third joint of outer ramus in fourth pair of feet more than twice as long as distal portion; 
outer margin of second joint not denticulate; proximal portion of outer margin of third joint of 
outer ramus in third and fourth pairs denticulate; scalpelliform 
terminal bristle of outer ramus in third pair longer than end joint; 
second joint of inner ramus of first pair with 5 bristles; third joint 
of inner ramus of second pair with 7 bristles; abdomen of female 
with 4 segments; last joint of anterior antennal less than 14 times 
as long as penultimate joint ; fifth foot short, 2-jointed ; right fifth 
foot of male 2-jointed, left 5-joiuted. 
Female: Head fused with first thoracic segment and fourth 
fused with fifth thoracic segment; rostrum ending in two llaccid 
threads; genital segment and furca symmetrical, the latter with- 
out an outer marginal bristle; anterior antennas 25-jointed, with 
obliterated separation between first and second, also between 
eighth and ninth joints; outer ramus of posterior antennre shorter 
than inner ramus; mandibles with broad blades; the sack-like 
appendage on first joint of inner ramus small ; maxillae with indis- 
tinct jointing of inner ramus, without a bristle on second outer 
marginal and with only one bristle on second inner marginal lobe; 
anterior maxilliped with an outer marginal bristle; inner ramus 
of first foot 2-joiuted, of the second to fourth 3-jointed. 
Male: Abdomen with 5 segments; number of joints in ante- 
rior antennae reduced by fusion of first to sixth and of seventh 
with eighth; terminal joint abbreviated but separated; :es the tasks 
enlarged and increased in number; mandibular blade, appendages 
of inner margin of maxillae and of anterior maxilliped, stunted; 
to a less extent also the posterior maxilliped, the outer bristle of which is long and densely plumose 
Minor peculiarities are also exhibited by the feet. 
6. Paracalanus parvus Claus; a, male, 
dorsal aspect; b, male, fifth pair of feet; 
c, female, fifth pair of feet. 
6. Paracalanus parvus Claus. 
Female: Inner bristle of furca scarcely longer than furca; anterior autenme reaching to posterior 
edge of third abdominal segment; first joint of inner ramus of maxillae with 2 bristles on anterior 
border; third lobe of first basal joint of posterior maxilliped with 2 bristles; inner margin of first 
basal of fourth pair of feet extending out into 1 or 2 points; anterior and posterior surfaces of 
first basal of second to fourth pairs of feet beset with hairs and points; surfaces of first and second 
joints of outer ramus of third pair and of second joint of inner ramus of fourth pair naked. 
Male: Abdomen with very short genital segment; feet longer than in female; mouth parts abbre- 
viated as in Calocalanus; sesthetasks present on some joints of anterior antennae where they are 
lacking in female; they are not very large on distal portion of antennae, but on joints 3 to 6 and 1 to 2 
they have the form of rather thick, long, dependent sacs; the bristles are short; fifth pair of feet 
similar to that of Calocalanus, but right foot has only 2 joints. 
