FREE-SWIMMING COPEPODS OF THE WOODS HOLE REGION. 
159 
dissect off the appendages, especially the feet, in order to determine the genus to which 
a particular form belongs. Permanent preparations of these or of the whole animals 
are easily made by simply adding a drop of Parrant’s medium to the sea water or 
formalin under the cover-glass. 
TABLE OF THE GENERA. 
[Genera represented in the Woods Hole fauna are indicated by an asterisk.] 
Inner ramus of first to third foot 3-jointed, of fourth foot 3-jointed to lacking. ( Arietellus , Augaptilus, 
Calaims * , Centropages *, Disseta, Heniicalanus, Heterochccta, Isias, Leuclcartia, Metridea* , Phyllo- 
pas, Pleuromma, AEgisthus, Clytemnestra* , Microselella, Monsirilla, Oithona*, Thaumaleus) A 
Inner ramus of first foot 3-jointed, of the second to fourth foot 2-jointed. ( Anomalocera *, Parapontella, 
Pontella *, Pontellina, Monops*, Corynura *) B 
Inner ramus of first foot 2-jointed, of the second foot 2 or 3 jointed, of the third and fourth foot 
3-jointed. ( Acrocalanus , Calocalanus * , Eucalanus *, Leuclcartia, Paracalanus*, Phincalanus, 
Temora*, AEgisthus, Euterpe, Mirada*, Seiella*) C 
Inner ramus of first to fourth foot 2-jointed. ( Acartia * , Calanopia, Candace*, Centropages *, Corynura *, 
Labidocera *, Temora *) D 
Inner ramus of first foot 1-jointed, of second to fourth foot 3-jointed (anterior anteunte about twice as 
long as ceplialothorax ; fifth foot with 3-jointed outer ramus and no inner ramus) . . Mecynocera* 
Inner ramus of first foot 1-jointed, of second foot 2-jointed, of the third and fourth foot 3-jointed. 
{Clausocalanus * , Ctenocalanus, Drepanopus, Gaetanus, Mcebianus, Phaenna, Pseudocalanus, Scole- 
cithrix, Spinocalanus, Xanthocalanus E 
Inuer ramus of first and second foot 1-joiuted, of the third and fourth foot 3-jointed. ( Aelidius , 
Chiridius, Euchceta, Eucliiriella, Undeuchwta) F 
1 mier ramus of first and second foot 1- or 2-jointed, of the third and fourth foot 1-jointed. . . Mormonilla 
A. Between anterior antennae and first pair of feet no appendages (Monstrillidai) A 1 
Between anterior antennae and first pair of feet usually all 5, or at least (Copilia $ ) 2 pairs of 
appendages (posterior antennae, posterior maxillipeds) A 2 
A 1. Anterior antennae not geniculating; ventral surface of genital segment with furcate, setiform 
appendage A 1 $ 
Anterior antennae geniculating; ventral surface of genital segment with a pulvilliform out- 
growth terminating in two lateral projections A1 
Al? Only 1 segment between the genital segment and the furca; furca with 3 bristles on either 
side Thaumaleus $ 
Two to 3 segments between genital segment and furca; furca with 5 to 6 bristles on either 
side Monsirilla $ 
A 1 $ Two segments between the genital segment and the furca; furca with 3 to 4 bristles on either 
side Thaumaleus $ 
Three segments between the genital segment and the furca; furca with 5 to 6 bristles ou either 
side Monsirilla $ 
A 2. Cephalothorax with 5 pairs of feet, the last of which is of variable structure and sometimes 
reduced to 1 or 2 joints. First abdominal segment without foot rudiments. Posterior 
antennfe biramous, their outer ramus with at least 5 joints; both rami with plumose or 
hooked bristles ( Gymnoplea in part) A3 
Cephalothorax with 4 pairs of feet. First (short) abdominal segment with rudiments of feet, 
which are inserted laterally or ventrally as paired (rod-, leaf-, or bristle-shaped) append- 
ages. Posterior antenme uni- or bi-ramous, in the latter case with at most 3-jointed, small, 
external ramus; tip of inner ramus with a few nonplumose, curved or hook-shaped bristles 
( Ampharthrandria in part) Isokerandria A 13 
A 3. On right or left sides of first thoracic segment in antero-lateral corner is a small brown 
knob Pleuromma 
With no such knob A 4 
A 4. First joint of inner ramus of the second foot with proximally curved hooks along the inner 
edge * Metridia 
First joint of inner ramus of second foot normal, resembling corresponding joint in other 
feet A 5 
