FISHERY BULLETIN: VOL 75, NO. 2 



o 

 ■o 



North 

 South 



America 

 America 



(N = 105) 

 (N= 127) 



-VA 



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22 23 24 25 26 27 28 



carapace length (mm) 



FIGURE 59. — Mesopenaeus tropicalis. Relationship between length of dorsal antennular flagellum and carapace length. 



inal elevation merging with convex terminal 

 portion; latter moderately long, its length 4-5 

 times basal width; lateral spines short, 0.9-1.4 

 times basal width of terminal portion; mesial 

 ramus of uropod reaching tip of telson or over- 

 reaching it by no more than 0.1 of its own length; 

 lateral ramus surpassing mesial ramus by 0.1-0.2 

 of its own length, and bearing small, terminal, 

 distolateral spine. 



Petasma (Figure 60A, B) cincinnulate along 

 proximal 0.7 of median line and with terminal 

 margin lacking spinules, often minutely rugose 

 across ventromedian lobule; distal portion of 

 ventromedian lobule thick, flexible, folded, its 

 mesial portion strongly excavate ventrally, and 

 overlying its shorter lateral portion; latter pro- 

 duced laterally into process resembling bird head 

 in silhouette, dorsolateral lobule with heavy rib 

 curved in hooklike terminal portion lying against 

 ventral surface of process; inner surface of dorso- 

 lateral lobule studded with minute setae mesially 

 and bearing proximolateral row of long setae; 

 corresponding, but shorter, row of long setae on 

 outer surface. Ventral costa reaching distally as 

 far as, or slightly overreaching, row of cincinnuli, 

 trending dorsally, and bearing flexible sub- 

 rectangular, marginal flap, extending horizon- 

 tally almost perpendicular to costa. 



Appendix masculina (Figure 60C, D) very elon- 

 gate, convex dorsally, deeply channeled ventrally, 

 its proximal part produced laterally into rounded, 

 ventrally turned lobe; distal part tapering, its tip 

 twisted mesiad, mesial surface deeply concave, 



and armed with densely set, relatively long setae 

 on proximolateral border, short setae on borders 

 of concavity, and tuft of long setae apically. 

 Appendix interna almost as long as appendix mas- 

 culina, broad, subelliptical, bearing lateral rib, 

 abutting corresponding border of appendix mas- 

 culina, and armed with tuft of long setae on disto- 

 lateral border, and very short setae on mesial 

 border. Basal sclerite obliquely crossed by heavy 

 ridge separating deep proximal concavity from 

 anterior depressed area, and with its ventro- 

 lateral spur proximally rounded and strongly 

 attenuate distally. 



Thelycum (Figure 61) with paired short, blunt, 

 cushionlike protuberances on flexible anterior 

 part of sternite XIV, contiguous to ventrally 

 raised, heavily sclerotized posterior shield; free 

 border of shield sharp or thickened, and varying 

 from slightly concave to produced into antero- 

 median, minute spine. Median plate of sternite 

 XIII divided by median longitudinal incision into 

 paired rounded to subrectangular lobes overhang- 

 ing sternite XIV, each bearing blunt horn antero- 

 lateral^. Sternite XII with paired blunt, distally 

 flattened projections overhanging sternite XIII. 



Photophores- Observations by me on freshly col- 

 lected specimens demonstrated that this species, 

 like H. affinis and H. debilis, bears photophores, 

 which are arranged as follows: one adjacent to the 

 base of the podobranchia of both the third maxilli- 

 ped and fourth pereopod, and a pair on the an- 

 terior part of the sternum from the second through 



336 



