FISHERY BULLETIN: VOL. 76, NO. 4 



along ventral outer margin; distal spine shortened 

 to about 0.1 X scale length. Protopodite retains 2 

 sharp ventral spines, larger about 0.6 x endopo- 

 dite length, smaller about 0.3 x length of larger. 



Mandibles: ( Figure 5C ). Incisor and molar pro- 

 cesses more developed; no palp. 



Maxillule: (Figure 5D). Endopodite un- 

 changed. Basal and coxal endites both with 5 

 spines, 3 setae. 



Maxilla: (Figure 5E). Endopodite unchanged. 

 Numbers and form of processes on either endite 

 little changed from earlier stage, with exception of 

 basal endite distal lobe; latter now with 1 spine, 4 

 strong setae, 1 thin seta. Scaphognathite with 10 

 marginal setae and usual thick apical seta. 



Maxillipeds 1 and 2: (Figures 5F, G). Coxal, 

 basipodal, dorsal and ventral endopodal, and 

 exopodal natatory setae as in previous stage. 



Maxilliped 3: (Figure 5H). Endopodite bud 

 now subequal to basipodite length, incipient seg- 

 mentation more prominent in some specimens 

 than others; exopodite with 7 natatory setae. 



Pereiopods: (Figure 2C, and detailed in- 

 set). More developed, many with incipient seg- 

 mentation; partial chelation of protochela often 

 visible. 



Abdomen: (Figure 2C, c). Six somites present, 

 sixth divided from telson; distinct lateral spine 

 remains only on somite 5; spinules on dorsal poste- 

 rior margins vestigial, ragged and irregular. In 

 some specimens small, amorphous swellings occur 

 ventrally on somites 2-5, signifying future posi- 

 tion of pleopod buds. 



Telson: (Figure 51). Marginal setal formula 

 remains 8-1-8; fourth pair of processes elongate 

 spines fused to telson; processes 3, 5-8 retain 

 noticeable hooklike spinules distally; other dorsal 

 setae as illustrated. Uropods present at junction of 

 abdominal somite 6 and proximal margin of tel- 

 son; exopods of same well developed, with variable 

 number of marginal plumose setae (usually about 

 8); endopods, if present, merely foreshortened 

 naked buds. 



Color: More distinctly colored than stage II. 

 794 



Orange chromatophores: dorsally on interior 

 margin of eyestalks, a single orange spot on 

 carapace laterally, just above each maxilliped 1, 

 another small grouping laterally on abdominal 

 somite 2; diffused orange on antennular peduncle, 

 ventrolaterally on carapace below eyes, interiorly 

 on mouthparts and within gut region, and on en- 

 dopodites of maxillipeds 1-3. Red chromatophores: 

 on cutting edge of mandibles, dorsomedially and 

 laterally on abdominal somite 4, laterally on so- 

 mite 5, the latter appearing as if small drops of 

 blood. 



Fourth Zoea (Regular) 



Carapace length: 1.4 mm. 



Number of specimens examined: 10. 



Carapace: (Figure 2D, d). Rostral spine with 

 noticeably raised lateral margins, greatly ex- 

 panded basally at point of attachment to carapace, 

 slightly overreaching scaphocerite spine and an- 

 tennular exopodite; carapace posterolateral and 

 dorsomedial margins unarmed; posterior spines 

 quite short, hooked downward. Eyes large, on 

 elongated stalks. 



Antennule: (Figure 6A). Exopodite with three 

 rows of lateral aesthetascs, numbering distally 

 2-3, 3, 2-3, in addition to usual 3, plus 3 setae, at 

 tip. Endopodite about 0.5 x length of exopodite, 

 plumose seta absent. Protopodite retains distal 

 lateral setal, plus usual 4 stout setae at junction of 

 exopodite; 3 medial, 2 basal setae now also pres- 

 ent. 



Antenna: (Figure 6B). Endopodite elongate sub- 

 equal to scaphocerite length; latter bearing 10-12 

 (numbers variable on left and right appendages in 

 same specimen) marginal setae plus numerous 

 ventral spinules on outer margin. Larger pro- 

 topodal ventral spine about 0.3 x endopodite 

 length, smaller about half size of larger; armature 

 of both remains as in earlier stages. 



Figure 6. — Galathea rostrata, fourth zoeal appendages: (A) 

 Antennule , regular stage; ( a ) same , advanced stage; ( B ) antenna, 

 regular stage; (b) same, advanced stage; (C) mandibles, regular 

 stage; (c) same, advanced stage; (D) maxillule; (E) maxilla; (F) 

 maxilliped 1; (G) maxilliped 2; (H) maxilliped 3; (I) telson; all 

 regular stage; (i) detail, fifth telsonal process, 40 x objective. See 

 test for discussion. Scale lines total 0.3 mm. 



