PEREZ FARFANTE: ROCK SHRIMP GENUS SICYONIA 



mesial base of distolateral spine; latter long, 

 reaching as far as distal 0.25 of second antennular 

 article; antennular flagella short, mesial one, 

 more slender and shorter than lateral, 0.20-0.30 as 

 long as carapace; lateral flagellum 0.25-0.35 as 

 long. 



Scaphocerite surpassing antennular peduncle 

 by no more than 0.1 its own length; lateral rib 

 ending distally in long, acute spine conspicuously 

 overreaching margin of lamella. Antennal flagel- 

 lum about twice as long as carapace. 



Third maxilliped stouter than pereopods. Basis 

 and ischium of first pereopod unarmed. 



Abdomen with dorsomedian carina extending 

 from first through sixth somites, carina on first 

 produced in strong, anteriorly inclined tooth, ta- 

 pering suddenly near end to minute, sharp apex 

 (usually broken and thus appearing blunt); tooth 

 considerably larger than posterior one on car- 

 apace; carina on fifth somite abruptly truncate or 

 produced in sharp tooth posteriorly, and that on 

 sixth terminating in strong, acute posterior tooth. 



Antero ventral margin of ple\iron on first abdom- 

 inal somite concave in adults, sometimes nearly 

 straight in juveniles, its extremity ending in 

 strong spine, that of second through fourth (in 

 adults) often projecting slightly or forming ven- 

 trally pointed spine; posteroventral extremity of 

 third through sixth somites sharply angular, that 

 of third often, but in last three always bearing 

 caudally directed spine, that of fifth and sixth 



largest and smallest, respectively; additional 

 spine occasionally present immediately dorsal to 

 posteroventral one on fourth somite. 



First abdominal somite marked with short, deep 

 anteromedian pleural sulcus and long, united 

 posterior tergal-posteromedian pleural sulci; 

 short, longitudinal ridge extending between an- 

 teromedian pleural and posterior sulcus. Second 

 and third somites with anterior tergal sulcus join- 

 ing united posterior tergal-posteromedian pleural 

 sulci dorsally, and with anteromedian pleural sul- 

 cus represented by shallow depression setting off 

 elevation at dorsal extremity. Fourth and fifth so- 

 mites bearing curved, united posterior tergal- 

 posteromedian pleural sulci; sometimes fourth 

 also with faint anterior tergal sulcus. Sixth somite 

 often marked by weak, sometimes indistinct, 

 arched, posteromedian sulcus and bearing con- 

 spicuous cicatrix frequently divided in two. 



Telson with median sulcus well defined only 

 along anterior 0.65 of its length and armed with 

 pair of minute, fixed, subterminal spines; latter 

 clearly developed in juveniles but vestigial or lack- 

 ing in adults. Rami of uropod subequal in length, 

 falling slightly short of or barely overreaching 

 apex of telson. 



Posterior spine on first abdominal sternite with 

 wide base and usually concave but sometimes 

 straight lateral margins. 



Petasma (Fig. 55A, B) with cornified distal pro- 

 jection of dorsolateral lobule raised in prox- 



FIGURE 55. Sicyonia disdorsalis , 6 17 mm cl, off Balboa, Panama. A, Petasma, dorsal view; B, ventral view of same; C, right 



appendix masculina, dorsolateral view. Scales = 1 mm. 



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