FISHERY BULLETIN: VOL. 83, NO. 1 



lapping plate of sternite XIV but areas im- 

 mediately lateral to it flush with preceding plate. 



Color. — The specimen examined by me from Peru 

 exhibits a dark colored mask in the shape of a "2" 

 (the base situated anteriorly), disposed hori- 

 zontally from the posterolateral part of the 

 carapace onto the anterodorsal part of the first 

 abdominal pleuron. 



Maximum size. — Male 12.7 mmcl, about 43.5 mm 

 tl; female 20 mm cl, 65.5 mm tl. 



Geographic and hathymetric ranges. — In addition 

 to the undetermined type-locality, "St. Joseph" 

 (most probably San Jose, Baja California), it has 

 been found in Bahia Aimejas (24°29'18"N, 

 111°47'24"W) and off Cabo San Lucas, both on the 

 ocean side of Baja California Sur, in Bahia de la 

 Paz, on the eastern side of the latter, off Isla 

 Taboga in the Golfo de Panama, and off Puerto de 

 Eten (6°22'S, 80°47'W), Peru (Fig. 12). Sicyonia 

 mixta occupies shallow water at depths between 11 

 and 24 m. 



The discovery of S. mixta first in the Golfo de 

 Panama and more recently northwest of Puerto de 

 Eten, Peru, was surprising and represented a con- 

 siderable extension of the range of the species. 

 F*reviously, it was known only from the waters of 

 Baja California, where the three male types were 

 collected and where, in Bahia de la Paz, five 

 females and a male were found (Rodriguez de la 

 Cruz 1977). The specimen from off Puerto de Eten 

 (a female 20 mm cl, 26.5 mm tl ) was collected by M. 

 Niquen from the RV Humboldt on 27 April 1983, 

 and is deposited in the IMARPE. 



Discussion. — As Burkenroad (1946) stated, S. 

 mixta is unique in lacking a tooth on the anterior 

 end of the dorsomedian carina of the first abdomi- 

 nal somite. Also this shrimp exhibits two of the 

 basic characters of the species that Burkenroad 

 (1934a) grouped in his Division II (the presence of 

 a well -developed or clearly distinct antennal spine 

 and the absence of basial and ischial spines on the 

 first pereopod) at the same time that the dorsome- 

 dian carina of the second abdominal somite, al- 

 though not incised, is abruptly depressed an- 

 teriorly. This depression seems to represent the 

 deep incision or notch typical of the species of his 

 Division I. 



Among the American species (excluding those 

 grouped in Division I), S. mixta, S. disedwardsi, 

 S. penicillata, and two western Atlantic species 



24 



— S. typica (Boeck 1864) and sometimes S. olgae 

 Perez Farfante, 1980 — possess three dorsal teeth 

 on the postrostral carina, two of which are situ- 

 ated posterior to the hepatic spine. In S. mixta, 

 however, the posterior tooth arises on the post- 

 rostral carina considerably in advance of the pos- 

 terior margin of the carapace, and the carina ends 

 markedly anterior to the margin; in the other 

 species the tooth arises nearer the margin where 

 the carina ends. Sicyonia mixta also differs strik- 

 ingly from the other four in the general sculp- 

 ture of the abdomen; whereas in S. mixta it is not 

 tuberculate and lacks all pleviral sulci except the 

 anteromedian on the first somite and the postero- 

 median on the sixth, in these congeners the ab- 

 domen is strongly tuberculate, exhibits deeper 

 sulci, and possesses pleural sulci and all sixth so- 

 mites. The bifurcate shape of the terminal part 

 of the distal projection of the ventrolateral lob- 

 ule of the petasma is another character that dis- 

 tinguishes S. mixta from the just mentioned rela- 

 tives. 



The relationships of this species are rather 

 puzzling. Except for the distinctly depressed dor- 

 somedian carina of the second abdominal somite, 

 it does not share any other characters of impor- 

 tance with the species of Division I, represented by 

 S. disparri, S. laevigata, and S. parri. Actually, it 

 appears to be much closer to the group represented 

 in the eastern Pacific by S. disedwardsi and S. 

 penicillata, for in addition to possessing an anten- 

 nal spine and lacking spines on the basis and is- 

 chium of the first pereopod, like them, it is armed 

 with two teeth on the postrostral carina posterior 

 to the hepatic spine. It seems to me that S. mixta 

 has had, although remotely, a common origin with 

 the above-mentioned group. 



Remarks. — Because females of this shrimp have 

 not been known previously, the above description 

 of the thelycum is the first available for this 

 species. In addition to the females cited from the 

 Golfo de Panama and off northern Peru, two other 

 new records are presented here: one represented 

 by a male from off Cabo San Lucas, Baja Califor- 

 nia Sur, and the other by a female from Bahia 

 Aimejas, Gulf of California. These four specimens, 

 the types, and the six reported by Rodriguez de la 

 Cruz (1977) are the only ones that have been re- 

 corded for this shrimp. 



The holotype of this species and the paratype, in 

 the Naturhistorisches Museum (Vienna), are the 

 only extant types of the Sicyonia treated here that 

 were not examined by me. 



