FISHERY BULLETIN: VOL. 83, NO. 1 



tunity to examine all except two of the extant 

 type-specimens of the species have made a critical 

 study of the genus in the eastern Pacific possible. 

 The present work includes a definition of the genus 

 and a key to the species occurring in the region. A 

 complete synonymy and usually complete list of 

 references, vernacular names, and a diagnosis 

 precede the detailed description of each species, 

 which includes a discussion of the extensive varia- 

 tion exhibited as well as meristic and morphomet- 

 ric data. In addition, relation of the length of the 

 rostrum to the length of the carapace is graphed 

 for 10 species. Color notes, size range at which 

 males reach adulthood, and minimum size 

 at which females have been observed to be im- 

 pregnated are given. Geographic and bathymetric 

 ranges are delimited, and ecological data are pro- 

 vided. Analyses of the diagnostic features utilized 

 in the recognition of species and a discussion of 

 their phylogenetic relationships are also pre- 

 sented. Distributional maps as well as illustra- 

 tions of entire animals, genitalia, and a few other 

 morphological features are included along with a 

 bibliography which is as complete as possible. A 

 statement of their economic importance follows 

 the treatment of the pertinent species, and a list of 

 the specimens examined, with their localities, is 

 appended to each of the 12 species. 



The distributional studies have resulted in ex- 

 tensions of both geographic and bathymetric 

 ranges of several species; e.g., of the seven species 

 known to occur both in the Gulf of California and 

 on the ocean side of the peninsula, five have not 

 been previously reported from the latter, and one, 

 which had been recorded only as far north as Point 

 Conception, Calif., was found to reach Monterey 

 Bay (Perez Farfante and Boothe 1981). Of the 12 

 species that have been reported from the region, 10 

 (or 11, in the unlikely event that the presence of S. 

 affinis is confirmed) occur in the Gulf of California; 

 of those occurring in the gulf, S. disparri appears 

 to be virtually confined to it and only S. ingentis 

 extends northward beyond Mexico, along the coast 

 of the United States. Eight of the 10 species range 

 southward to Central America, and of them 4 

 reach as far as Peru and S. aliaffinis also occurs off 

 Islas Galapagos. Sicyonia brevirostris has been 

 reported exclusively from the Golfo de Tehuan- 

 tepec, and S. affinis is known with certainty only 

 from Costa Rica to Colombia. 



Seven of the species, S. laevigata, S. mixta, S. 

 disedwardsi, S. penicillata, S. aliaffinis, S. mar- 

 tini, and S. picta, appear to have disjunct ranges. 

 None has been recorded from stretches variable in 



extension within the limits cited herein, and all of 

 the gaps encompass areas off southern Mexico. 

 Perhaps the discontinuities are due to limited 

 exploratory investigations; however, one species, 

 S. disdorsalis, has been found to occur virtually 

 continuously from the Gulf of California to Peru. 

 Nevertheless, speculations attempting to explain 

 the apparent gaps in the ranges of these species 

 should await the confirmation of their existence. 



Except for records of the occurrence of S. picta at 

 333 m (Faxon 1893) and 369-400 m (Arana Espina 

 and Mendez G. 1978) and S. brevirostris at 329 m 

 (Williams 1965), no other species were previously 

 known from depths greater than about 200 m; here 

 six others are reported between about 250 and 300 

 m, depths considerably greater than their previ- 

 ously known maximum occurrence. 



Distributions of members of the genus Sicyonia 

 in the eastern Pacific appear to differ strikingly 

 from those of most species of the closely related 

 family Penaeidae in that region. Whereas some 

 species of Sicyonia are restricted to comparatively 

 small areas (one confined to the southern and gulf 

 coasts of Baja California and waters immediately 

 south), others range from the Gulf of California to 

 the northern or to the central coasts of Peru. Most 

 of the eastern Pacific species, like their western 

 Atlantic congeners, reveal a marked preference for 

 firm or coarse bottoms. 



PRESENTATION OF DATA 



Many characters used in the descriptions are 

 depicted in Figures 1-7. To provide an appreciation 

 of the structure of the eye and the nomenclature 

 employed in its description I have chosen that of S. 

 disedwardsi. To illustrate the first article of the 

 antennular peduncle and anterior gnathal append- 

 ages, S. ingentis was selected. The petasmata 

 have been drawn from specimens stained with fast 

 green. For convenience, both the armature of ster- 

 nite XI and the shape of the posterior thoracic 

 ridge are presented with the description of the 

 thelycum. Scales accompanying the illustrations 

 are in millimeters. The length of the rostrum (rl) 

 recorded herein is the linear distance from the 

 apex to the orbital margin; length of the carapace 

 (cl) is the distance between the orbital margin and 

 the midposterior margin of the carapace; and the 

 total length (tl) is the distance from the apex of the 

 rostrum to the posterior end of the telson. The 

 geographic distribution of each of the species pre- 

 sented on the maps is based on material personally 

 examined and on published records believed to be 



