P6REZ FARFANTE: ROCK SHRIMP GENUS SICYONIA 



recently Perez Farfante and Boothe (1981) added 

 S. martini^ as possessing two teeth posterior to the 

 orbital margin, of which one, that posterior to the 

 level of the hepatic spine, is large. Like all mem- 

 bers of Division II, in S. affinis the antennal spine 

 is buttressed, but the buttress is barely distinct in 

 contrast to that in S. aliaffinis and S. martini in 

 which it is well developed. In S. affinis the first 

 rostral tooth is situated farther anteriorly, at 

 about the end of the anterior third of the rostral 

 length from the orbital margin, than in the other 

 two species in which it is placed opposite or im- 

 mediately anterior to the orbital margin. 



In S. affinis the abdominal surface is punctate 

 but otherwise rather smooth, lacking tubercles, 

 conspicuous ridges, and deep sulci. Also, in S. 

 affinis the anteromedian sulcus of the first abdom- 

 inal somite is not only weak but short, whereas in 

 S. aliaffinis and S. martini it is deep (except ven- 

 trally in S. martini in which it is represented by a 

 shallow depression) and long, in S. aliaffinis al- 

 most reaching the ventral margin of the pleuron. 

 The anteromedian sulci of the second and third 

 somites in S. affinis are distinct only ventrally, 

 rather than dorsally as in S. martini, or along 

 most of the height of the somite, as in S. aliaffinis. 

 The posteromedian sulci of these somites in S. 

 affinis extend dorsally only to a point situated at 

 about 0.33 of the height of the somite from the 

 dorsal midline where they turn anteriorly and are 

 marked dorsally by weak longitudinal ridges; 

 these sulci are considerably shorter than the well- 

 incised ones in S. aliaffinis, which extend to about 

 the dorsal 0.25 of the height of the somite, and are 

 not accompanied dorsally by longitudinal ridges. 

 In S. martini the posteromedian sulci curve an- 

 teroventrally at their dorsal ends, defining strong 

 angular ridges. 



As Burkenroad (1934a) pointed out, in iS. affinis 

 the dorsal carina of the fifth abdominal somite 

 does not end in a sharp angle or acute tooth as it 

 does in the other two species; instead its posterior 

 part slopes gradually to the apex of the caudal 

 cleft. In S. affinis the tip of the tooth on the first 

 abdominal somite is slightly curved anteriorly 

 whereas in S. martini it forms a conspicuous hook, 

 and in S. aliaffinis the entire tooth is straight and 

 projects anterodorsally Furthermore, the antero- 

 ventral extremities of the pleura of the first four 

 somites in S. affinis are unarmed whereas they 

 bear a small spine in S. aliaffinis , and in S. mar- 

 tini, although lacking spines, are strongly angular 

 instead of faintly so or rounded as they are in S. 

 affinis. 



These three species can also be distinguished 

 readily by petasmal and thelycal characters. In S. 

 affinis the projection of the dorsolateral lobule of 

 the petasma, like that of S. aliaffinis, is truncate 

 or shallowly emarginate distally and produced in 

 a simple, dorsally directed, sharp salient, whereas 

 in S. martini the projection curves gently to a 

 conspicuously bifurcate, mesially directed tip; on 

 the other hand, in S. affinis, as in S. martini, the 

 projection of the ventrolateral lobule is fiattened 

 and curved or concave dorsally rather than being 

 strongly bulbous as it is in S. aliaffinis. In the 

 females of S. affinis and S. martini the thelycal 

 plate of sternite XIV bears a pair of low but well- 

 marked lateral bulges (longitudinally disposed in 

 the former and transversely so in the latter), 

 whereas in S. aliaffinis the plate is almost flat or 

 barely raised in ill-defined elevations. Moreover, 

 in both S. affinis and S. aliaffinis, the posterior 

 emargination of the median plate of sternite XIII 

 does not embrace a tubercle, as it does in S. mar- 

 tini. 



Material. — 17 specimens from 6 lots. 



Costa Rica— 3c5 59, AHF, 4.4 km off Isla Ma- 

 nuelita, 146 m, 3 June 1973, Velero IV stn 

 19044. 16 , syntype, USNM, off Isla del Coco, 95 

 m, 28 February 1891, Albatross stn 3369. 16 19, 

 syntypes, MCZ, off Isla del Coco, 183 m, 28 Feb- 

 ruary 1891, Albatross stn 3367. 



Panama— 39, USNM, NE of Isla Iguana, 79-77 

 m, 4 May 1967, Pillsbury stn 515. 



Colombia — 19, syntype, MCZ, W of Isla de Mal- 

 pelo, 95 m, 5 March 1891, Albatross stn 3379. 29 , 

 syntypes, USNM, W of Isla de Malpelo, 205 m, 5 

 March 1891, Albatross stn 3378. 



Sicyonia aliaffinis (Burkenroad 1934) 

 Figures 38-42 



Eusicyonia aliaffinis Burkenroad, 1934a:92, fig. 24 

 [holotype 6, YPM 4393; type-locality: Pacific 

 coast of southern Mexico (NW of Puerto Ma- 

 dero), 14°48'40"N, 92°54'40"W, 19-30 fm (35- 

 55 m), 9 April 1926, Pawnee]. Burkenroad 

 1938:84, fig. 25, 27. Anderson and Lindner, 

 1945:317. 



Eusicyonia sp. Castro, 1966:17 [in part, by im- 

 plication]. 



Sicyonia aliaffinis. Chapa Saldana 1964: 

 15. Bayer et al. 1970:A97. Chirichigno 

 Fonseca 1970:7, fig. 6. Del Solar 1972: 

 7. Rodriguez de la Cruz 1977:10. Arana 

 Espina and Mendez G. 1978:25, fig. 6-9. 



47 



