1 cm. 



Figure 15. — Penaeiis (L.) schmitti 

 Burkenroad. Cephalothorax, 9 42 

 mm. C.I., Farol de Moela, Santcs, 

 Brazil. 



end of carpocerite or surpassing it as much as five- 

 sixths length of dactyl. Second pereopod reaching 

 from seven-ninths of first antennular segment to 

 one-third of second antemiular segment. Third 

 pereo]Dod exceeding antennular peduncle from % 

 to % of propodus. Fourth pereopod exceeding car- 

 pocerite from one-fifth to entire length of dactyl. 

 Fifth pereopod surjJassing fourth pereopod only 

 by about one-half length of dactyl. Exopods on all 

 pereopods; long ischial and basial spines on first 

 pereopod ; and ratlier long basial spine on second 

 pereopod. 



ABDOMEN 



Carinate dorsally from midlength of third or 

 from fourth somite posteriorly, carina gradually 

 increasing in height forming keel on sixth somite, 

 and ending in sharp spine on posterior margin of 

 somite. Dorsolateral sulcus very narrow, shallow, 

 and without lips. Sixth abdominal somite with 

 three cicatrices on each side, anterior one longest; 

 fifth somite with one cicatrix and diagonal series 

 of minute pits anterior to sinus on posterior margin 

 of somite; fourth somite with similar series of 

 pits dorsal to sinus on i^osterior margin of somite. 

 Ventral margin of pleuron of first somite mod- 

 erately to deeply indented. Telson unarmed, with 

 deep median sulcus and acuminate tip. 

 PETASMA (fig.l6 a-c) 



Lateral lobe with distal portion of inner sur- 

 face smooth, lacking diagonal ridge and fold; 

 distoventral corner of lateral lobe typically pro- 

 duced medially in subrectangular projection; an- 

 terior half of ventral border with two narrow ribs 

 joined at both ends. Emargination median to inner 

 lateral lappet relatively deep. Outer surface of 

 lateral lobe armed with broad band of very closely 

 set spines, as many as seven rows abreast distally 

 and decreasing to two proximally. Crests distally 

 on each side of band of spines, the one close to 

 median lobe moi-e prominent and sharp than that 

 near free ventral margin, latter crest bifurcate. 

 Lateral lobe often extending conspicuously beyond 

 median lobe. 



APPENDIX MASCULINA (fig. 16 d, e) 



Subtriangular. its length twice or slightly 

 greater than width at base, armed with short spines 

 along median margin and with long ones on distal 

 portion; distal spines slightly less than half length 

 of appendix. Anterior surface subplane, posterior 

 surface strongly concave, concavity bordered by 

 arch-shaped ridge. 



WESTERN ATLANTIC SHRIMPS OF GENUS PEXAEUS 



491 



