VoL. 2 Esterly— Copepoda of the San Diego Region. 1s 
or not. In the Podoplea some of the males have anterior erasp- 
ing antennae; in others this function is performed by the poste- 
rior antennae or posterior maxillipeds. 
The main axis of the appendages (excepting the anterior 
antennae) may be considered as parallel to the dorso-ventral 
diameter of the animal; accordingly anterior and posterior faces 
are distinguished in an appendage as well as proximal and distal! 
portions, and inner or outer margins of the various joints. 
This nomenclature is useful, especially since most appendages 
are flattened. The form, arrangement and number of the bristles 
on the appendages are used a great deal in identification. and 
for that reason the appendages must usually be dissected off. 
It is of importance to have only adult animals for study. 
The adult male in most genera has noticeable sexual peculiarities 
in the structure of the fifth feet or in the grasping antenna. 
The females are certainly adult if carrying eggs or spermato- 
phores. In large animals it is a comparatively easy task to dis- 
sect off the appendages, but in the majority of the Podoplea 
and the smaller Gymnoplea it requires a good deal of patience 
and a steady hand. A dissecting microscope is indispensable, 
and it is a good plan to use fine needles, which may be ground 
down to an edge. Farrant’s fluid makes a good mounting me- 
dium for permanent preparations. If it is spread thin over the 
slide the appendages may be placed in order in it and the cover 
glass put on without disturbing the arrangement. For the deter- 
mination of the genus of an individual the feet especially must 
be removed and examined. 
Most of the drawings in this paper were made with the aid 
of the Abbé camera. The keys, and descriptions of all but new 
species, are translated from Giesbrecht’s works of 1892 and 1898. 
In the general key for the Gymnoplea the plan adopted in the 
Tierreich (1898) has been followed, but only those genera are 
included which from their distribution might be expected to 
occur in the San Diego region. Species keys are given in some 
eases, but include only the species actually found; however, if 
one sex of a form occurs, and the other has not been obtained, a 
description of the latter is given in most cases. 
