FISHERY BULLETIN: VOL. 73, NO. 3 



premarginally. The posterolateral membranous 

 extension is reflexed and attached to the rib dor- 

 sally, thus forming a shallow pocket. After the 

 compound spermatophore is deposited on the 

 thelycum, the pockets of the paired wings come to 

 lie posteromesially and are quite conspicuous on 

 those impregnated females in which the geminate 

 body has been lost. 



Thelycum (Figure 1 1 ) 



Sternite XIV bears a large median sub- 

 pyramidal prominence with a subtriangular base 

 (broad anteriorly, tapering posteriorly), its sharp 

 midlongitudinal carina armed with a row of very 

 minute setae. The highly sclerotized posterior part 

 of sternite XIII is produced into a rigid, subver- 

 tical shelf overhanging sternite XIV; this shelf 

 constitutes the posterior wall of a pair of concavi- 

 ties which are separated by a sharp median ridge 

 and are delimited anteriorly and laterally by 

 strong angular paired ridges, the posterior bases 

 of which extend laterally and bear toothlike 

 projections. The anterolateral part of sternite XIII 

 bears paired transverse rigid elevations covered 



by long setae. Heavily sclerotized sternite XII is 

 nearly straight along its posteromedian margin, 

 and produced caudally in a pair of lateral projec- 

 tions armed with tufts of setae. The conspicuous 

 concavities of sternite XIII serve to lodge the 

 sperm masses which emerge from the ruptured 

 anterodorsal bulges of the compound sperma- 

 tophore. 



Disposition of the Compound 

 Spermatophore on the Thelycum 



When the compound spermatophore is in posi- 

 tion on the female, the anterior extremity of the 

 geminate body lies on the ventrally turned mesial 

 borders of the coxal plates of the third pereopods, 

 with the sperm masses (projecting through the 

 anterodorsal bulges) lodged in paired thelycal 

 concavities of sternite XIII, near the gonopores 

 (Figure 12). The wings contribute to anchoring the 

 spermatophore: their anterior regions are at- 

 tached to the posteroventral surfaces of the coxae 

 of the third pereopods, the mesial portions follow- 

 ing the contour of the strongly curved coxal plates; 

 lobes borne on the dorsal side of the anterior 

 regions certainly function as adhesive elements. 

 The posterior region of each wing is extended 



PKStJRE ll.-Penaeus (Litopenaeus) styliroatris. Thelycum, 946 

 mm cl, off Bella Vista, Panama. 



Figure i2.—Penaeus (Litopenaeus) stylirostris. Sternites XII 

 and XIII bearing paired masses of sperm and wings of a com- 

 pound spermatophore, the geminate body of which has been lost 

 (see explanation in text), 9 48 mm cl, off Guaymas, Mexico. 



474 



