fourth pereopod. Exopods on all pereopods. Long 

 iscliial and basial spines on first pereopod; rather 

 long basial spine on second pei'eopod. 



ABDOMEN 



Carinate dorsally from posterior half of fourth 

 somite posteriorly, carina gradually increasing in 

 height to form keel on sixth somite, ending in 

 sharp spine on posterior margin. Dorsolateral sul- 

 cus (fig. 62) extremely narrow, ratio between 

 lieight of keel and width of sulcus from about 

 3 to 16, modally 6 (fig. 63) ; K/S ratio showing 

 same modal value of 6 for all sizes of both sexes 

 (fig. 64) ; dorsal and ventral lips both sharp. Sixth 

 abdominal somite with three cicatrices on each side, 

 anterior the longest, posterior very small. Fifth 

 abdominal somite witli one cicatrix and row of 

 minute pits anterior to sinus on posterior margin 

 of somite. Fourth abdominal somite witli similar 

 row of minute pits dorsal to sinus on posterior 

 margin of somite. Telson unanned, with deep 

 median sulcus and sharp pointed tip. 



PETASMA (fig. 55 a, b) 



Ventral costa slightly curved witli distal por- 

 tion blunt, bearing group of 6 to 12 (modal 6) 

 irregiUarly set teeth close to apex, its free distal 

 margin even or with faintly undulating flange, 

 apex adnate to ventrolateral lobule. Ventrolateral 

 lobule with band of spines consisting of single row 

 or pair of rows distally, with three to six series of 

 spines extending proximally to about midlength 

 of lobule. Doi-solateral lobule often with single 

 row of widely spaced minute spines along midline. 

 Distomedian projections relatively short, slightly 

 overhanging distal portion of ventral costae. 



FiGUEE 62. — Penaciis (SI.) paulensis Perez Farfante. 

 Sixth abdominal somite, posterodorsal portion, holotyiie, 

 $ 35 mm. e.l., Santos, Sao Paulo, Brazil. 



Figure C3. — Percentage of distribution of keel-sulcus 

 (K/S) values in Pcnaeus (i/.) paulensis Perez Far- 

 fante. 



APPENDIX MASCULINA (fig. 65c) 



Sliglitly elongated, lengtlx I14 to IV3 maximum 

 widtli, witli long spines projecting from distome- 

 dian margin and with slightly concave lateral 

 margin armed with short, strong spines. Anterior 

 surface subplane or slightly convex, posterior sur- 

 face strongly concave, with sharp longitudinal 

 ridge along median margin. 



THELYCUM (fig. 66) 



Anterior process narrow, projecting ventrally 

 in .subtriangular or highly arched ridge, surround- 

 ing shallow depression with minute knob usually 

 present at center. Posterior process with median 

 carina bifurcate anteriorly, resulting ribs turning 

 medially and converging at base of anterior proc- 

 ess, giving rise to very narrow diamondlike struc- 

 ture. Lateral ])lates witli anteromedian corners di- 

 vergent, leaving posterior process exposed. 



558 



U.S. FISH AND WILDLIFE SERVICE 



