Figure 11. — Penaeua duorarum Burkenroad. A, carapace 

 and eyes of animal in dorsal view, "Form A" from 

 Xorth Carolina, natural size; B, petasma of adult male, 

 distal portion, view from right side ; C, thelycum of 

 adult female; B-C, 1 mm. indicated (after Burkenroad, 

 1039). Chromatophore distribution in tail fan (semi- 

 diagrammatic) of D, 17 mm. juvenile, E, 32 mm. 

 juvenile: D-E, approximately X .", (after Williams, 

 1953). 



Female with thelycum composed of two broad 

 lateral plates, and a median plate. Posteromedian 

 part of median plate of adult with a well- 

 developed, short, longitudinal carina extending 

 anteriorly toward roughly semicircular, concave 

 anterior portion. Lateral plates produced medially 

 to meet in midline, except variably divergent at 

 anteromedian corners, thus exposing carina of 

 median plate. 



Abdomen with segments four to six carinate, 

 carina of sixth ending posteriorly in a spine ami 

 Hanked on each side by a narrow groove. Telson 

 with deep median groove and an acuminate tip. 



Petasma of male with distal ends of distoventral 

 lobes curved medially, not projecting free of dis- 

 tolateral lobes; external edge of distoventral lobes 

 with a series of 2 to 12, usually 4 to 7, small 

 spinules; median or attached edge of distoventral 

 lobes with a compact group of 6 to 16 large, long, 

 sharp, curved spines; fold of distolateral lobe 

 rather small and armed inconspicuously if at all. 



Measurements. — Length of body : large male, 

 167 mm.; large female, 210 mm. 



Variations. — Burkenroad (1939) divided the 

 species into two "Forms," "A" and "B." 



In "Form A" the dorsolateral grooves of the 

 sixth abdominal segment usually are almost or 

 entirely closed, though they may be open to a 

 width of one-third the distance from their dorsal 

 lip to the midline. 



In "Form B" the dorsolateral grooves of the 

 sixth abdominal segment are broadly open, their 

 width being from one-half to more than equal the 

 distance from their dorsal lip to the midline. 



The rostrum is relatively shorter and deeper 

 in old individuals than in young ones. It extends 

 to the end of the basal antennular article in 

 average-sized adults. The rostrum in P. duorarum 

 is less sinuous and slender than in P. aztecus. 



Color. — Juveniles and young adults from estu- 

 aries or oceanic water near shore are usually gray, 

 reddish brown or bluish gray of various shades, 

 with a more or less distinct spot of darker color 

 at the pleural juncture of the third and fourth 

 abdominal segments. In juveniles or young adults, 

 this spot and other bandings may be graj', blue 

 gray, blue, or purplish. The tail fan is nearly 

 transparent and edged with blue. In older in- 

 dividuals, especially from deeper oceanic water, 

 the colors tend to be red, pinkish-, blue gray or 

 nearly white. The abdominal spots are usually 

 red (Broad, 1950) or lacking entirely. Detailed 

 coloration of the young has been given by Wil- 

 liams (1953). 



Habitat. — Estuaries and inner oceanic littoral, 

 predominantly on sand, shell-sand or coral-mud 

 bottom from water's edge to 28 fathoms; rarely 

 40 to 200 fathoms (U.S. Fish and Wildlife Serv- 

 ice, 1960). 



Type locality. — Off Alabama [Atlantis station 

 2813, roughly lat. 30° N. long. 88° W.), 19 

 fathoms. 



22 



FISH AND WILDLIFE SERVICE 



