PfiREZ FARFANTE: ROCK SHRIMP GENUS SICYONIA 



12 18 24 



carapace length (mm) 



30 



Figure 40. — Sicyonia aliaffinis. Relationship between rostrum 

 length and carapace length (regression equation for specimens 

 with about 16 mm cl or less,^' = 0.83950 + 0.25635x; regression 

 equation for those larger, y = 2.34086 + 0.13665x). 



tending from orbital margin almost to end of ros- 

 trum. 



Carapace with strong postrostral carina bear- 

 ing two teeth: 1) epigastric tooth small, subequal 

 to or slightly larger than first rostral tooth, 

 situated opposite or anterior to level of hepatic 

 spine, between 0.15 and 0.22 (mean 0.18) cl from 

 orbital margin; and 2) posterior tooth, much 

 larger, as much as three times higher than epigas- 

 tric, hooklike, its apical portion acutely pointed 

 and strongly curved anteroventrad; tooth placed 

 well in advance of posterior margin of carapace, 

 between 0.66 and 0.76 (mean 0.71) cl from orbital 

 margin. Postrostral carina slightly elevated just 

 in front of posterior tooth and forming high crest 

 from latter descending gently to posterior margin 

 of carapace. Tuft of setae present at anterior base 

 of each tooth. Antennal spine sharp, projecting 

 from well-marked buttress; hepatic spine acute, 

 larger than antennal, arising from raised area, 

 and situated between 0.19 and 0.26 (mean 0.23) cl 

 from orbital margin. Postocular sulcus deep an- 

 teriorly, continuing posteriorly as low groove; 

 hepatic sulcus well marked; branchiocardiac 

 carina distinct but rather low, extending longitu- 

 dinally from hepatic region almost to posterior 

 margin of carapace, there bifurcating: one branch 

 curving dorsally and other disposed ventrally. 



Antennular peduncle with stylocerite produced 

 in long spine, its length about 0.9 distance be- 

 tween lateral base of first antennular article and 

 mesial base of distolateral spine; latter extending 

 to about midlength of second article. 



Scaphocerite almost reaching or slightly over- 

 reaching distal margin of antennular peduncle; 

 lateral rib produced distally in long, strong spine 

 surpassing distal margin of lamella. Antennal 

 flagellum as much as 2 times as long as carapace. 



Abdomen with high dorsomedian carina ex- 

 tending from first through sixth somites, carina on 

 first somite produced in strong triangular tooth as 

 high as, or usually higher (as much as one-third) 

 than, posterior tooth on carapace, its anterior 

 margin straight, subvertical or sloping anterodor- 

 sally; carina on fourth somite obliquely truncate 

 posteriorly forming obtuse (rarely almost right 

 angle); that on fifth strongly truncate forming 

 acute posterior tooth; and that on sixth strongly 

 produced in large acute posterior tooth. 



First four somites with angular anteroventral 

 extremity bearing small spine; fourth somite with 

 posteroventral extremity broadly angular, occa- 

 sionally armed with minute spine, and fifth and 

 sixth somites with posteroventral extremity bear- 

 ing small sharp spine, that of fifth slightly larger. 



First somite marked with long anteromedian 

 pleural sulcus joining coalescent posterior 

 tergal-posteromedian pleural sulci near margin of 

 pleuron. Second and third somites with deep an- 

 terior and posterior tergal and long, well-incised 

 anteromedian (expanding ventrally) and pos- 

 teromedian pleural sulci, posteromedian ones ex- 

 tending dorsally to a point located at least at 0.25 

 of the height of the somite from the dorsal midline. 

 Fourth somite bearing anterior and posterior ter- 

 gal sulci, posterior one merging with deep, long 

 posteromedian sulcus. Fifth somite marked with 

 anterior tergal sulcus and united posterior 

 tergal-posteromedian pleural sulci. Sixth somite 

 with short anterior tergal sulcus, strongly arched 

 posterior pleural one, and setose, longitudinal de- 

 pression delimited dorsally by rib and ventrally by 

 usually strong cicatrix. 



Telson with pair of small but well-developed 

 fixed spines. Rami of uropod subequal in length, 

 reaching or slightly overreaching apex of telson. 



Petasma (Fig. 41) with rigid distal projection of 

 dorsolateral lobule curved mesially, raised prox- 

 imodorsally in rounded prominence, and com- 

 pressed distally; its truncate tip with ventral ex- 

 tremity rounded and dorsal extremity sharply 

 produced in minute spine. Fleshy distal projection 

 of ventrolateral lobule with firm, terminal part 

 directed laterally almost at right angle, dorsally 

 bulbous, ventrally flat, and tapering to pointed, 

 ventrally inclined apex. 



Petasmal endopods coupled in males 8.2 mm cl, 



49 



