morphology. Additionally, there are some genera that 

 cannot be identified using only one sex. For example, 

 females o( Amonardia. Amphiascopsis. and Metamphia- 

 scopsis are indistinguishable and generic separation is 

 based entirely on male dimorphic characters, while in 

 other genera the males are indistinguishable and separa- 

 tion is based entirely on female morphology. In the key I 

 have tried to use characters common to both sexes; how- 

 ever, such characters are often not very useful and in 

 some cases I have had to use either a male or female 

 character to specifically designate a genus. 



The harjiacticoid body surface is often ornamented 

 with minute sensilla, fine hairlike filaments projecting 

 outward through the cuticle. These structures are often 

 found banding the animal and have important tax- 

 onomic significance in intrageneric systematics but will 

 not be discussed in detail here. 



The cephalon (head) bears five pairs of appendages 



(standard abbreviations in parentheses after the append- 

 age name): aniL-nnules (A,), antennae (A ), mandibles 

 (Md), maxillulae (or 1st maxillae, Mxl), and maxillae (or 

 2nd maxillae, Mx). Projecting forward from the anterior 

 end of the cephalosome between the A,'s is usually a 

 rostrum. The rostrum varies in size from as long as the 

 first three A, segments to minute and barely visible. The 

 rostrum may have a distinct articulation with the 

 cephalon (i.e., defined at the base) or it may be fused to 

 the cephalon with no articulation and therefore not 

 defined at its base. The first two thoracic somites, which 

 are usually fused to the cephalon (forming the above 

 defined cephalosome), also bear appendages, i.e., the 

 maxillipeds (Mxp) and the first legs (P, ). The remaining 

 thoracic somites bear legs 2-4 (P,-P, ). The urosome 

 starts with the somite bearing the 5th legs (PJ and ex- 

 tends to the caudal rami (see Figure 2 for generalized 

 harpacticoid with appendages). 



Figure 2.— Ventral and lateral views of a Keneralized harpacticoid topepod with body parts 

 labeled. A, = antennule; .\ - antennae; Md = mandible; Mxl = maxillula; .Mx = maxilla; Mxp = maxil- 

 liped; I^ -P = legs 1-.5. In the ventral view only one pair of legs is drawn per somite. Each somite, of course, 

 has a pair of legs, but for the sake of clarity only alternative sides are drawn. 



3 



