80 U.S. NATIONAL MUSEUM BULLETIN 2 36 



16. Basis of maxillipede twice as long as wide 17 



Basis of maxillipede V/i times as long as wide 21 



17. Baso-endopodite slender, at least as long as broad, reaching halfway along 



exopodite H. poppei Richard 



Baso-endopodite of leg 5 broader than long, reaching maximally Yz the length 

 of exopodite 18 



18. Basis of maxillipede at apex with internally directed spiniform process. 



H. tenellus G. O. Sars 

 Basis of maxillipede normally developed 19 



19. 2nd segment endopodite of leg 2 with 2 internal setae. 



H. septentrionalis Klie 

 2nd segment endopodite of leg 2 with 1 seta at internal border .... 20 



20. Exopodite of leg 5 long and slender, 3 times as long as wide, internal and 



external border parallel H. clausi A. Scott 



Exopodite not more than twice as long as broad, ovate. 



H. obscurus T. Scott 



21. Furca very short, 4 times wider than long H. falldandi T. Scott 



Furca about twice as wide as long 22 



22. Basis of maxillipede deeply concave H. gracilis Glaus 



Basis of maxillipede deeply incised to form square notch. 



H. littoralis G. O. Sars 



MALES 



1. Furca IH times or more longer than wide 2 



Furca about as long as wide or wider than long 3 



2. Furca more than twice as long as wide H. furcifer Giesbrecht 



Furca maximally 1^2 times longer than wide H. furcatus Lang 



3. Basis of maxillipede internally straight or convex 4 



Basis of maxillipede internally deeply concave or incised with square notch. 5 



4. Terminal segment of endopodite leg 1 with 2 claws and 1 plumose seta. 



H. siiperflexus Willey 

 Terminal segment of endopodite leg 1 with 2 claws and 1 nude seta. 



H. flexus Brady 



5. Antenna with pectinate spines 6 



Antenna with normally developed spines 7 



6. Appendages on terminal segment of exopodites legs 2 to 4, number 7, 8, 



and 8, respectively H. pulvinatus Brady 



Appendages on terminal segment of exopodites legs 2 to 4, number 6, 

 7, and 8, respectively H. compsonyx Monard 



7. 1st segment of exopodite leg 3 lengthened, reaching beyond articulation 



between segments 2 and 3 of endopodite . . . H. chelifer (O. F. Mliller) 



1st exopodal segment of leg 3 shorter, not reaching the articulation between 



segments 2 and 3 of endopodite 8 



8. Segment 2 of exopodite leg 2 lengthened, much longer than segment 1 



of same exopodite H. falklandi T. Scott 



Segments 1 and 2 of exopodite of leg 2 of nearly the same length 9 



9. Anterior aspect of segments 1 and 2 of endopodites legs 3 and 4 with small 



spines H. obscurus T. Scott 



Anterior aspect of endopodites legs 3 and 4 nude or segment 2 of endopodite 



legs 3 and 4 with 3 thin spinules 10 



10. Exopodite leg 1 distinctly 3-segmented . . . . H. meridionalis G. O. Sars 

 Exopodite of leg 1 indistinctly 3-segmented or only 2-segmented .... 11 



