PSEUDOCYCLOPS COPEPODS—BOWMAN AND GONZALEZ 39 
joint, slender and plumose distal to joint. Exopod segments 1 and 2 
with 1 inner seta and 1 outer seta; segment 3 with 1 terminal seta, 
2—2-3-3 inner setae, and 4—5—5—5 outer setae; endopod segment 3 with 
6-8-8-7 setae on legs 1-4 respectively. Female leg 5 with 3-seg- 
mented exopod and endopod of 1-3 segments; exopod segment 3 with 
3 outer setae, distal one apparently terminal, and terminal seta 
inserted slightly medial to apex and often curving medially; inner 
setae often reduced in number or absent. 
Leg 5 of male forming a complex grasping organ. Right exopod 
unisegmental, bearing a short flanged outer spine and 2 long spines 
curving inward; right endopod unisegmental, unarmed. Left exopod 
2-seemented; proximal segment bearing a flanged spine, distal seg- 
ment bearing membranous appendages; left endopod unisegmental, 
often bearing several plumose setae at the apex; a slender elongate 
appendage arises from left second basipod adjacent to endopod. 
Key: The four new Puerto Rican species described below can be 
distinguished by the key below. Our key is purposely based on 
characters that can be observed without dissection, but it may be 
necessary to examine cleared specimens with a compound microscope. 
Since the genus Pseudocalanus appears to be highly endemic, the key 
is reliable only in the vicinity of the type locality and should be used 
with caution elsewhere: 
MYVeHead and: first*pedigerous segment fused':? 272; 2°%. 794.6 20 Ra Ae 2 
Head and first pedigerous segment notfused. . ... . abye 3 
2. Rostrum very large; second pedigerous segment Penined mate process 
ventrolaterally; caudal setae with barbs. . .. . : . . . Yrostratus 
Rostrum of monere te size; second pedigerous segment rounded ventrolater- 
ally; caudal LBP maith out barbs (iho = 2 4. 3 cokeri 
3. Length 0.50-0.62 mm.; prosome with red bend) or gaan: all red; male 
rostrum articulated st base; endopod of female leg 5 3-segmented. 
rubrocinetus 
Length 0.37—0.43 mm.; body colorless; male rostrum not articulated at base; 
endopod of female leg 5unisegmental. ........... =. paulus 
RELATIVE ABUNDANCE: In one tow through the turtle grass, all 
the specimens of Pseudocyclops obtained in the sample were enumer- 
ated as to species and sex with the following result: 
Species Female Male 
cokert a2i1 154 
rubrocinctus 63 3 
paulus 44 8 
rostratus 0 0 
P. rostratus is quite rare in all our collections. It is possible that 
our method of collection does not sample the main habitat of P. 
rostratus but only collects a few individuals on the periphery. 
EcouocicaL nicHE: We have observed the behavior of living 
specimens of the species of Pseudocyclops described below, with the 
