dopod. The portions most often lacking on the various 

 mouthparts are the endopods and the exopods but there 

 is no generalization that can be made as to when or in 

 what genera these parts will be lacking or reduced. For a 

 more complete morphological description and differen- 

 tiation of these parts, the reader should see Lang (1948, 

 1965). 



Legs 1-5 (P, -P5 ) are the most widely used appendages 

 for taxonomy. Legs 1-4 are generally constructed in a 

 similar manner, whereas leg 5 is usually fused and 

 morphologically dissimilar from the others. Therefore, P5 

 will be dealt with separately. FJ -P^ are generally con- 

 structed with a coxa, a basis, an outer exopod (Exp), and 

 an inner endopod (Enp) (Fig. 6). The coxa attaches to 

 the ventral side of the body on either side of the midline 

 with the basis attaching to it. The exopod and endopod 

 vary in length, the number of segments and setation 

 depending on the species. The example in Figure 6 il- 

 lustrates 3-segmented rami, which is probably the most 

 advanced condition of the order. In many species, the en- 

 dopod of P, is modified as a prehensile appendage where 

 segment 1 is usually much longer than segments 2 and 3 

 combined and segment 3 generally terminates with one 

 or two recurved setae reminiscent of a claw. Functionally 

 this appendage is most likely used for grasping and cling- 

 ing to substrates and is most highly developed in the 

 phytal forms. In the benthic forms it is probably used to 

 grasp and turn over sediment particles and perhaps to 

 hold the particles while scraping them with the 



mouthparts. Besides changes in leg segmentation, the P^ 

 and/or P3 endopod is usually different in the male than it 

 is in the female. The male endopod may be one segment 

 shorter than the female's and terminally modified into 

 either a spatulate, spear, or clawlike process. Figure 8 il- 

 lustrates one such dimorphic modification. 



All five pairs of legs may be ornamented with com- 

 plements of setae, spines, hairs, spinules, setules, knobs, 

 denticles, ridges, and other chitinous prolusions. The 

 terms "spine" and "setae" are used for short stiff 

 processes and for long flexible processes respectively, and 

 are the most important leg armature characters for iden- 

 tification of the animal. Setae and spines are noted in the 

 diagram of the typical harpacticoid leg (Fig. 6). Most 

 harpacticoid taxonomists use a system of numbers to 

 depict the spine and setal arrangement known as the 

 setal formula. This is arrived at by counting the number 

 of inner (medial) setae and spines of each segment of 

 each ramus up to the last segment and then counting all 

 the setae and spines on the last segment of the ramus. 

 For example, if we were to arrive at a setal formula for 

 the typical harpacticoid leg in Figure 6, we would count 

 the inner setae on the first endopod segment (1); the in- 

 ner setae on the second endopod segment (21; the inner 

 setae on the third endopod segment (3); the terminal 

 setae on the third endopod segment (2); and the outer 

 (lateral) setae on the third endopod segment (1). For the 

 exopod we would count the inner setae on segment one 

 ( 1 ) ; the inner setae on segment two ( 1 ); the inner setae on 



8 



DANIELSSENIA EASTWARDAE COULL 



Figure 8.— The second leg (P ) of a female and male DanieUennia ecutwardae. Note the sexual dimorphism. 



6. 



