P6REZ FARFANTE: ROCK SHRIMP GENUS SICYONIA 



trally, but its dorsal extremity often not reaching 

 anterior margin. Second and third somites with 

 anterior and often short posterior tergal sulci; an- 

 teromedian pleural sulcus frequently joining 

 posteromedian pleural sulcus (sometimes obso- 

 lete) dorsally, and continuous with anteroventral 

 depression setting off prominence dorsally and 

 ridge posteriorly. Traces of posterior pleural sulcus 

 occasionally present in one or more of first three 

 somites. Fourth and fifth somites with anterior 

 tergal joining curved, united posterior tergal- 

 posteromedian pleural sulci. Sixth somite with 

 shallow, arched posteromedian pleural sulcus; 

 longitudinal ridge along base of dorsomedian 

 carina delimited ventrally by weak depression 

 lying dorsal to ill-defined cicatrix. 



Telson with pair of small but clearly distinct 

 fixed spines. Rami of uropod subequal in length 

 and falling slightly short of or overreaching apex 

 of telson by as much as 0.15 its own length. 



Petasma (Fig. 28A, B) with rigid distal projec- 

 tion of dorsolateral lobule mesially inclined (in- 

 stead of erect), strongly curved dorsomesially then 

 laterally; distal part of projection slightly com- 

 pressed, often bearing crest, rounded ventrally 

 and produced laterally in elongate, acutely 

 pointed salient. Distal projection of ventrolateral 

 lobule with terminal part strongly curved later- 

 ally, bulbous dorsally, plane ventrally, with 

 pointed tip curved proximoventrally. 



Petasmal endopods coupled in males with 

 carapace length as little as 5.5 mm (about 22.5 mm 

 tl), but sometimes unjoined in individuals with 

 carapace length as much as 10.5 mm (about 38.5 

 mm tl). These observations are similar to those 

 noted by Burkenroad (1938). 



Appendix masculina as illustrated in Figure 

 28C. 



Thelycum (Fig. 29) with plate of sternite XIV 

 raised in paired, low (sometimes indistinct), rela- 

 tively short bulges, sloping toward deep, broad, 

 median depression. Median plate of sternite XIII 

 sagittiform, tapering gradually into long, slender 

 spine reaching as far as proximal 0.25 of basis of 

 extended second pereopods; plate deeply excavate 

 and bearing arched lateral incisions at level of 

 fourth pereopods; posterior component with deep, 

 broad posteromedian emargination forming rela- 

 tively elongate, posterolateral processes marked 

 basally by rather faint transverse suture. Sternite 

 XI armed posteriorly with pair of small, broad 

 based spines. Posterior thoracic ridge either al- 

 most flush with plate of sternite XIV or with only 

 anteromedian margin raised (ventrally). 



Sperm receptacles as illustrated in Figure 7 (il- 

 lustration based on specimen treated following 

 method by Monod and Cals (1970)). 



The smallest impregnated female encountered 

 has a carapace of 12 mm, about 42 mm tl. 



Color. — The only observation on color of fresh 

 material from the Gulf of California (Anonymous 

 1980) indicates that the typical large spot found in 

 the posterior part of the branchiostegite is 

 purplish brown with a yellow center. The con- 

 spicuous ocellate spot persists in preserved speci- 

 mens, appearing like a broad dark ring surround- 

 ing a light center. 



Maximum size. — Male, 29.2 mm cl, about 102 mm 

 tl; female 34 mm cl, about 108 mm tl. 



Geographic and bathy metric ranges. — Southwest 

 of Isla Santa Margarita (24°19'36"N, 111°46'24"W 

 - 24°19'48"N, 111°47'06"W) to Bahia San Lucas, 



Figure 29. — Skyonia disedwardsi , 9 21.3 mm cl, off Punta 

 Gorda, Baja California Sur, Mexico. Thelycum. Scale = 2 mm. 



35 



