(1962) also described a series of larval and post- 

 larval stages from eggs hatched and reared under 

 laboratory conditions in Mississippi. 



Ryan (1956) summarized life history data for 

 R. harrisii in the Chesapeake Bay area. Ovigerous 

 females were collected from June to September 

 (also in April in Louisiana and Brazil). Though 

 juveniles were found in all months of the year, 

 they occurred most frequently in samples taken 

 from July to October. Immature forms of unde- 

 termined sex ranged from 2.2 to 2.6 mm. in width. 

 Immature males ranged from 3.2 to 5.0 mm. and 

 similar females from 3.3 to 5.7 mm. in width. 

 Ryan considered maturity to be reached the fol- 

 lowing summer at a carapace width of 4.5 mm. 

 for males and 4.4 to 5.5 mm. in females. 



Adults continue to grow and molt after ma- 

 turity is reached, and males finally attain a larger 

 size than females (up to 14.6 and 12.6 mm. wide 

 respectively). No concrete data on number of in- 

 stars throughout life are available but it is esti- 

 mated that there may be four instars between at- 

 tainment of the 5 and 10 mm. carapace widths. 



This species has been transported from its 

 original range to two widely separated areas of 

 the earth. One of these is the west coast of the 

 United States where it was reported in the San 

 Francisco Bay area by Jones (1940) and Filice 

 (1958), and at Coos Bay, Oreg., by Ricketts and 

 Calvin (1952). An older and wider introduction 

 in Europe was reviewed by Buitendijk and Hol- 

 thuis (1949) who considered the European form a 

 separate subspecies (R. h. tridentatus (Mait- 

 land)). Originally confined to the old Dutch 

 Zuider Zee, the species gradually diminished in 

 abundance there with the closing of that inland 

 sea in 1936. In that same year it was first reported 

 outside Netherlands waters. In 1939 it was first 

 reported in large numbers from southern Russia 

 in the Dnjetr and Bug River estuaries, and ac- 

 cording to fisherman there was first observed in 

 1936 but certainly not present before 1932. The 

 latest extension of range was reported by Wolff 

 (1!>54) in South Harbor of Copenhagen, Den- 

 mark. 



Because this form is easily collected and can 

 tolerate a low but broad range of salinities, it has 

 been the subjeci of study in investigations on the 

 mechanism of osmoregulation (Jones, L941; Ver- 

 wey,1957). 



Genus Hexapanopeus Rathbun, 1898 



Rathbun, 1930a, p. 383. 



KEY TO SPECIES IN THE CAROLINAS 



a. Carpus slightly tuberculate angustifrons (p. 188). 



aa. Carpus tuberculate paulensis (p. 189). 



Hexapanopeus angustifrons (Benedict and Rathbun). 

 Narrow mud crab 



Figures 170, 183D 



Panopeus angustifrons Benedict and Rathbun, 1891, p. 373, pi. 

 22, fig. 3 ; pi. 24, fig. 18. 



Hexapanopeus angustifrons: Hay and Shore, 1918, p. 43,fi, pi. 

 34, fig. 7.— Rathbun, 1930a, p. 384, pi. 169, figs. 1-2 (rev.). 



Recognition characters. — Carapace hexagonal, 

 about two-thirds to three-fourths as long as wide, 

 convex from front to back, regions fairly well 

 marked, surface finely granulate. Anterolateral 

 edge thin, upturned, and divided into five teeth, 

 first two separated by a well-defined sinus, third 

 and fourth successively broader, fifth shorter, nar- 

 rower, more distinctly directed outward; each of 

 last two teeth with a ridge extending obliquely in- 

 ward and backward for distance twice length of 

 teeth. Front narrow, produced, divided in half 

 by a prominent V-shaped notch; each half bilo- 

 bate, with markedly sinuate anterior border form- 

 ing a broad inner and small, inconspicuous outer 

 lobe. 



Figure 170. Bewapanopeus angustifrons (Benedict and 

 Rathbun). A. animal in dorsal view; B, large chela 

 in frontal view; 5 mm. indicated. 



INS 



FISH AND WILDLIFE SERVICE 



