as in males. Body heights are alike in the two 

 sexes. 



Spines. — All spiniform characters, poorly de- 

 veloped and rounded at the apices in juveniles, 

 gradually assume conformation characteristic of 

 the species as growth progresses. 



Chelipeds. — All species in the genus have the 

 hands of the chelipeds (Figures 3-17) modified 

 into a major chela (crusher, usually on right side) 

 and a minor chela (cutter, usually on left side) — 

 heterochelic and heterodont (Schafer, 1954; 

 Stevcic, 1971). Loss of the major chela induces 

 a well-known reversal at the next molt with the 

 new hand becoming a minor chela. A few indi- 

 viduals have two minors, but almost none exhibit 

 two major chelae. Size and strength of the major 

 hand vary a good deal, each species having a some- 

 times ill defined but characteristic shape. In all, 

 especially among males, the dactyl of the major 

 chela has a strongly developed proximal tooth 

 which closes against a molariform complex on the 

 propodus (Schafer, 1954). A decurved lower mar- 

 gin near the base of the propodal finger opposite 

 the proximal crushing apparatus on opposed edges 

 of the fingers accompanies development of the 

 complex, and in huge males of some species is a 

 prominent feature. Teeth distal to the molariform 

 complex of the major chela are more sectorial in 

 structure, but not so sharp as those on the minor 

 hand. Sectorial teeth of both hands tend to be 

 arranged in triads, a large central tooth flanked by 

 smaller ones, but there is much variation. In old 

 individuals no longer molting or molting infre- 

 quently, the proximal crusher teeth become worn, 

 occasionally almost obliterated. Size and wear 

 vary with species and are undoubtedly associated 

 with feeding habits. Callinectes sapidus, for ex- 

 ample, is known to feed on the American oyster, 

 Crassostrea uirginica, and other mollusks. Other 

 species of Callinectes probably have similar feed- 

 ing habits, but these are not well documented. 



Secondary sexual structures. — Immature 

 females have a triangular abdomen (Figure 2) 

 with most segments indistinguishably fused, but 

 at the terminal maturation molt (Churchill, 1919) 

 all segments become free. The abdomen of mature 

 females has a variable but roughly characteristic 

 shape in each species. Distal portions of the abdo- 

 men in immature males also have a developing 

 shape which becomes characteristic of the species 

 in adults. 



FISHERY BULLETIN: VOL. 72, NO. 3 



Primary sexual structures. — The copulatory ap- 

 paratus of male Callinectes has been recognized as 

 a good separator of species since the time of Ord- 

 way (1863), but until recently no one used fine 

 structure of these organs as serious aid to 

 identification. Snodgrass (1936) and Cronin 

 (1947) both described the external male sexual 

 apparatus, and I here adopt Snodgrass's term 

 "first gonopod" for the first male pleopod. The first 

 gonopod is essentially a narrow flat plate rolled 

 longitudinally into a cylinder that may be vari- 

 ously curved and twisted, terminating in a tip 

 varying from nearly tubular to a simply flared 

 trough. First gonopods of each species have 

 characteristic shapes, but there is individual vari- 

 ation reinforced by age, molt stage, wear, and 

 irregularity in preservation. The distal portion of 

 each first gonopod is armed with retrogressive ar- 

 ticulated spinules, exceedingly tiny and rather 

 unevenly distributed in one set of species having, 

 short first gonopods — C. gladiator Benedict 

 (1893), marginatus A. Milne Edwards (1861), or- 

 natus Ordway (1863), andsimilis Williams (1966) 

 (Figures 18a-d, 20a-d), as well as in a second set 

 with relatively longer first gonopods — C. arcu- 

 atus Ordway (1863), danae, and exasperatus (Ger- 

 staecker, 1856) (Figures 18e-g, 20 e-i), but larger 

 and arranged in longitudinal bands among species 

 with long curved first gonopods in a third set — 

 C. bellicosus, bocourti, latimanus Rathbun (1897), 

 maracaiboensis Taissoun (1972), rathbunae 

 Contreras (1930), sapidus, and toxotes Ordway 

 (1863) (Figures 18h-j, 19, 20j-p, 21). In the last 

 group, the spinules are irregular in size show- 

 ing evidence of breakage and replacement during 

 growth. Moreover, first gonopods of certain species 

 bear slender setae. In C arcuatus and danae, with 

 first gonopods of moderate length, the setae are 

 subterminal (Figure 20e-h) but in others with 

 longer first gonopods [C. bellicosus, latimanus, 

 maracaiboensis, rathbunae, sapidus, and toxotes 

 (Figures 20j-p, 21)] they are arranged along the 

 shaft at levels between the fifth to seventh 

 thoracic sternites in a single sternomesial row 

 following the twist of the appendage. The setae are 

 relatively largest in bellicosus (Figure 20j, k). 



Structure of the female gonopores covered by 

 the abdomen and located near the midline on the 

 sixth thoracic somite (Snodgrass, 1936) is less use- 

 ful as a specific character than that of the male 

 first gonopod, but even here there are some con- 

 formational types. Each gonopore leads via a 

 spermathecal duct (vagina) to a spermatheca 



688 



