ANTENNULE (Figure 2C). — First antenna, 

 or antennule, conical and uniramous; bears eight 

 terminal aesthetascs (six long and two of inter- 

 mediate length); small budlike projection and 

 single aesthetasc subterminally. 



ANTENNA (Figure 2D). — Protopodite (spi- 

 nous process) of antenna elongate, about two- 

 thirds length of rostral spine, armed with numer- 

 ous sharp spinules that increase in size distally; 

 exopodite slender, less than one-half length of 

 protopodite, two setae near sharp tip, each seta 

 with two rows of many fine setules; endopodite 

 naked, about two-thirds length of exopodite. 



MANDIBLES (Figure 2E). — Right and left 

 mandibles nearly identical; palps unjointed and 

 naked; incisor composed of two large, rounded 

 processes. 



MAXILLULE (Figure 2F). — First maxilla, or 

 maxillule, bears coxal and basial endites and an 

 endopodite. Proximal lobe (coxopodite) bears nine 

 spinulose spines, eight terminally and one sub- 

 terminally. Median lobe (basipodite) bears nine 

 spines distally: two setose spines, three simple 

 spines, four spinous spines (especially stout) plus 

 a large setose seta proximally Endopodite two- 

 segmented, originates from lateral margin of 

 basipodite, bears seven setae (six on distal seg- 

 ment, one on distal margin of proximal segment). 



MAXILLA (Figure 2G). — Bears platelike 

 exopodite (scaphognathite) with 21-23 plumose 

 setae along outer margin; no long, thick seta at 

 proximal end. Endopodite unsegmented, bears six 

 setae distally and fine hairs along outer margin. 

 Basipodite bilobed; each lobe bears six setae. 

 Bilobed coxopodite bears eight setae, four on each 

 lobe. 



FIRST MAXILLIPED (Figure 2H). — Exopo- 

 dite completely segmented; bears six heavily 

 plumose (natatory) setae on distal end. Endopo- 

 dite five -segmented; setation formula 4, 3, 1, 2, 3. 

 Basipodite bears 10 setae along posterior edge, all 

 setae except natatory setae sparsely plumose. 



SECOND MAXILLIPED (Figure 21). — Exopo- 

 dite completely segmented, bears six long, heav- 

 ily plumose (natatory) setae terminally. Endopo- 

 dite three-segmented, setation formula 5, 1, 1. 

 Basipodite bears four setae along posterior mar- 

 gin, all except natatory setae, sparsely plumose. 



THIRD MAXILLIPED (Figure 2J). — Not fully 

 developed, unsegmented, bilobed. 



FIRST PEREOPOD (Figure 2K). — Chela 

 segmented from carpopodite, bilobed but not 

 functional. 



SECOND TO FIFTH PEREOPODS. — Small, 

 uniramous, not segmented or bilobed. 



ABDOMEN AND TELSON (Figure 2A, L). — 

 Abdomen consists of six somites and telson. So- 

 mites 1-5 bear pair of simple setae middorsally; 

 somites 2-5 also bear pair of simple setae near 

 dorsal posterior margin. Second and third somites 

 both bear pair of curved lateral processes; length 

 of pair on second somite about half the height 

 (Figure 2 A) of second somite; pair on third somite 

 about half the length of pair on second somite. 

 Pair of long well-developed spines on posterior 

 lateral margins of third, fourth, and fifth somites; 

 those on third and fourth somites extend beyond 

 posterior margin of adjacent somites to about 

 midpoint of fifth and sixth somites, respectively. 

 Spines on fifth somite extend to level of anus; lat- 

 eral spines usually bear a few minute spinules. 

 Undeveloped pleopods (Figure 2A) present on ab- 

 dominal somites 2-5; length of pleopods about 

 three-fourths height of abdominal somites. Telson 

 bifurcate; furcations long, slender, finely spinu- 

 late, tips upcurved. Each furcation bears three 

 articulated telsonic setae and one simple seta on 

 mesial margin, a prominent spine laterally on 

 outer margin, a smaller dorsal spine posterior to 

 telsonic setae, and minute spinule about midway 

 between the lateral and dorsal spines; lateral and 

 dorsal spines on furcations minutely spinulate. 

 Each telsonic seta, except pair of simple setae, 

 bears two rows of spinules. Uropods (Figure 2A) 

 on somite 6 undeveloped, length about four- 

 tenths height of sixth somite. 



Comparison of North Pacific Zoeae of the 

 Subfamily Oregoniinae 



The subfamily Oregoniinae comprises three 

 genera, Chionoecetes, Hyas, and Oregonia (Garth 

 1958). Zoeae of the subfamily have been de- 

 scribed, at least in part, for C. opilio, C.japonicus, 

 H. coarctatus alutaceus, H. lyratus, and Oregonia 

 gracilis (Hart 1960; Kurata 1963; Yamauro 1968; 

 Haynes 1973; Motoh 1973). Based on these de- 

 scriptions. Stage I and II zoeae of the Oregoniinae 

 are readily separable from each other (Table 1). 

 Stage I zoeae are characterized by sessile eyes, 

 four natatory setae on the first and second maxil- 

 lipeds, absence of pleopods, and three pair of setae 

 on the inner margin of the telsonic furcations. 

 Stage II zoeae bear stalked eyes, six natatory 

 setae on the first and second maxillipeds, 

 pleopods, and four pair of setae on the inner mar- 



180 



