FISHERY BULLETIN: VOL. 83, NO. 1 



Baja California Sur, in the Gulf of California along 

 the central and southern parts of both coasts and 

 southward to Bahia Chamela (19°33'42"N, 

 105°07'24"W), Jalisco, Mexico. Also from Bahia de 

 Culebra (10°37'00"N, 85°40'00"W), Costa Rica, to 

 northwest of Punta Caracoles (7°45'00"N, 

 78°24'30"W), Darien, Panama (Fig. 30). It has 

 been found at depths between at least 18 (5-18) and 

 249 m, but seems to be most abundant at 30-60 m. 

 It occurs on bottoms of shell, mud, fine sand, and 

 rocks. 



The occurrence of this shrimp along the west 

 coast of Baja California Sur has not been previ- 

 ously reported. 



Discussion. — Sicyonia disedwardsi is most simi- 



FlGURE 30. — Geographic distribution of Sicyonia disedwardsi 

 and S. penicillata. 



lar to the western Atlantic S. typica. As stated 

 above, among the American members of the genus 

 lacking an incision or abrupt depression on the 

 middorsal carina of the second abdominal somite, 

 these two, together with S. penicillata and the 

 western Atlantic S. olgae bear two relatively large 

 teeth on the postrostral carina posterior to the 

 level of the hepatic spine. The genitalia of S. dis- 

 edwardsi and S. typica are so similar that they are 

 almost indistinguishable, but in the petasma of S. 

 typica the tip of the projection of the dorsolateral 

 lobule is not so strongly produced and is usually 

 directed dorsally rather than dorsolaterally. These 

 two species, however, differ in the number and 

 extension of abdominal sulci: in S. typica the first 

 three somites exhibit well-marked posterior 

 pleural sulci, which are absent or weak in S. dis- 

 edwardsi , and the dorsal extremity of the united 

 posterior tergal-posteromedian pleural sulci of the 

 first somite reaches the anterior margin of the 

 somite, whereas in S. disedwardsi the dorsal end 

 usually does not reach the margin. Also in S. 

 typica, the anteromedian pleural sulcus of the first 

 somite is unbroken and that of the second joins the 

 posteromedian, whereas in S. disedwardsi the 

 former is often interrupted and the median sulci 

 do not merge; in addition, the posterior tergal sulci 

 of the second and third somites are much longer 

 than in S. disedwardsi, in which they terminate 

 considerably dorsal to the base of the respective 

 pleuron. Furthermore, the rostrum of S. dised- 

 wardsi usually bears two teeth on the dorsal mar- 

 gin posterior to the apical teeth, whereas in S. 

 typica it is often armed with only one. 



Sicyonia disedwardsi differs from S. penicillata 

 by the same features of the abdomen that distin- 

 guish it from S. typica, except that in S. penicillata 

 the posterior pleural sulci are more frequently 

 present and slightly better marked than in S. dis- 

 edwardsi. Too, the rostrum of S. penicillata, like 

 that of S. typica, commonly bears only one dorsal 

 tooth and is less elevated and usually shorter than 

 in individuals of same size of S. disedwardsi. The 

 two partly sympatric species can be separated 

 readily by the genitalia. The unusually long distal 

 projections of the dorsolateral and ventrolateral 

 lobules in S. penicillata are not exhibited by any 

 other of its congeners. Also, whereas in S. dised- 

 wardsi the thelycal plate of sternite XIV bears 

 paired low (sometimes indistinct) bulges, in S. 

 penicillata it is raised in strongly marked and 

 more striking ones; the posterior component of the 

 median plate of sternite XIII in S. disedwardsi 

 exhibits a broad and deep posteromedian emar- 



36 



