50 

 40 

 30 

 20 

 10 

 

 40 

 30 

 20 



10 



z 

 s 



u 



Z 30h 



(/5 



O 20 



i 10 



z 





 30 

 20 

 10- 





 20- 



10 





 20 

 10 







C.I. 9-15 



N = 7I 



C.I. 16-22 



N=70 



C.I. 23-29 



N = 68 



C.I. 30-36 



N = 71 



C.I. 37-43 



N=43 



C.I. 44-58 



N=18 



2.5 4.5 6.5 8.5 10.5 12.5 14.5 



Figure 24. — Frequency distributiou of keel-sulcus 

 (K/S) values (both sexes included) in Pcnacus (If.) 

 (luorarum diioranim Burkenroad of different size 

 classes. 



APPENDIX MASCULINA (fig. 25 e-f) 



Broad, its length IV^q to ly^ maximum width, 

 armed with single row of strong spines along dis- 

 tal two-thirds of concave lateral margin, and with 

 thi'ee rows of longer spines along distal and 

 median margins. Anterior surface slightly con- 

 vex, posterior surface strongly concave, with 

 sharp ridge projecting from median margin. 



THELYCUM (figs. 26 and 27) 



Anterior process relatively large, bordered by 

 strongly convex, sharp ridge, surrounding rather 

 strongly concave ventral surface. Posterior process 

 bearing single, prominent, median carina, extend- 

 ing anteriorly toward anterior process. Lateral 

 plates with median appressed border raised as a 

 ridge or lip; rounded or slightly projecting an- 

 teromedian corners diverging, leaving median 

 carina exposed. Seminal receptacle dorsal to later- 

 al plates provided witli median slitlike opening; 

 latter corresponding to fissure between plates. 

 COLOR 



Color of P. d. duorarum is variable. Specimens 

 from the Tortugas and Campeche commercial 

 grounds are generally pink, and fishermen in those 

 areas refer to this subspecies as "i^ink shrimp" 

 and "camaron rosado," respectively. Large indi- 

 viduals from the northern Gulf of Mexico fre- 

 quently have a grayish color, and brownish speci- 

 mens are also common in inshore waters. Young 

 shrimp are also of a clear gray, whitish, green, or 

 pink coloration, and some are almost colorless. 

 Tlie pink coloration is often deep, and the live-bait 

 shrimp dealers along both coasts of Florida call 

 this subspecies "red shrimp." Williams (1953) de- 

 scribed freshly caught juveniles from North Caro- 

 lina as having the uropods with chromatophores 

 scattered uniformly, reddish brown distally and 

 blue along the creases. The uropods of the sub- 

 adult are almost transparent, with a light Ijlue 

 margin. 



P. d. duorarum very often has a reddish or pur- 

 plish brown spot on each side at the juncture of 

 the third and fourth abdominal somites — hence, 

 the common names pink-spotted, brown-spotted, 

 or simply spotted slirimp. Many specimens, how- 

 ever, lack abdominal spots, and. when present, the 

 spots usually fade and become invisible after 

 death. This shrimp also shows concentrations of 

 chromatophores that darken certain areas, like 

 narrow bands anterior to the })osterior margin of 

 the carapace and abdominal somites, as well as 



506 



U.S. FISH AND WILDLIFE SERVICE 



