onyx macrocheles (Gibbes) , should have to under- 

 go a name change, but Haig (1956) has shown 

 that Porcellana macrocheles Gibbes, 1850, is a 

 homonym of Porcellana macrocheles Poeppig, 

 1836, hence unavailable. The substitute name is 

 quite appropriate, however, for it not only honors 

 the original describer but is applied to a species 

 common in the area where he worked. 



Unlike other porcellanids occurring in the 

 Carolinas, Polyonyx gibbesi has been the subject 

 of some ecological observations. Enders (1905), 

 at Beaufort, N.C., and Pearse (1913), at Woods 

 Hole, Mass., studied commensal inhabitants of the 

 tubes of Chaetopterus variopedatus, finding P. 

 gibbesi to be common commensals in both areas. 

 Both authors found usually a male and a female 

 crab in the same tube, but Enders found six 

 isolated ovigerous females in the course of a 

 summer. Pearse found the species to be strongly 

 thigmotactic, and crabs, seemingly too large to 

 enter Chaetopterus tubes, entered and left an 

 artificial tube at will in the laboratory. 



Individuals usually moved backward or side- 

 ways on open sand, using the chelipeds as an aid 

 in walking, or at times swam clumsily upside 

 down by flapping the abdomen. Individuals 

 showed little ability to burrow. The respiratory 

 mechanism seemed well adapted to life in confine- 

 ment, for the respiratory currents were strong and 

 capable of being directed, changing with the 

 change in direction of waterflow in the worm tube. 

 Crabs in an experimental tube tolerated consider- 

 able fouling of the water. 



Pearse gave an excellent figure of the detailed 

 structure of the chelate and tufted fourth walking 

 legs which are used extensively in the meticulous 

 preening characteristic of this species. The plumes 

 of hairs on the appendages, especially those on the 

 third maxillipeds, are used as nets for capturing 

 food from water currents. 



Gray (1961) reviewed the life history and ecol- 

 ogy of the species. He found that the breeding 

 season at Beaufort, N.C., extends at least from 

 April to December, and ovigerous females are 

 otherwise known in February and March from 

 Florida. Usually when a pair of P. gibbesi is 

 found in a tube, adult crabs of no other species 

 are present at the same time. The smallest female 

 with eggs was 8.4 mm. in width. Gray concluded 



that the crabs enter worm tubes by chance, not in 

 response to attractants. 



In the years since Enders' and Pearse's studies, 

 the proportion of Pinnixa chaetopterana to Poly- 

 onyx gibbesi at Woods Hole and Beaufort has 

 changed. Woods Hole; Polyonyx-Pinnixa; 1913, 

 22:78; 1959, 66:34. Beaufort; 1905, 83:17; 

 1958-59, 39: 61. Gray (1961) postulated that the 

 more southerly species, P. gibbesi, has increased in 

 the Woods Hole area due to amelioration of cli- 

 mate. In the Beaufort area, decline may be due to 

 recent hurricane damage which destroyed many 

 Chaetopterus tubes. Gray also found that P. gib- 

 besi prefers less muddy bottoms than P. chaetop- 

 terana. He considered P. gibbesi an obligate com- 

 mensal of Chaetopterus. 



Faxon (1879) discussed the last stage zoea of P. 

 gibbesi and determined that it molts directly into 

 the first crab stage with no intervening megalops 

 as in brachyurans. Smith (1880b) reported 

 swarms of zoeae of P. gibbesi at the edge of tidal 

 currents near the mouth of Narragansett Bay in 

 summer. 



Superfamily Paguridea 



Carapace elongate and subcylindrical, or broad 

 and crablike ; front not fused with epistome. Ab- 

 domen soft, asymmetrical, and spirally coiled, 

 merely bent or flexed against thoracic sterna as in 

 Brachyura, or rarely symmetrical, straight and 

 well calcified dorsally. Tail fan usually present 

 and asymmetrical, occasionally symmetrical. Eyes 

 never in orbits. Antennal peduncle five jointed; 

 second article almost always with a movable 

 acicle. First pair of legs chelate and usually 

 large; fifth pair always, and fourth pair com- 

 monly, much less developed than preceding pairs. 

 Abdominal appendages usually unpaired on sec- 

 ond to fourth, or second to fifth segments, and 

 usually present only on left side (Alcock, 1905). 



Family Paguridae. Hermit crabs 



Carapace usually somewhat elongate and 

 broadened posteriorly, sides membranous, and 

 covered with a network of very thin lines ordi- 

 narily limited above by linea anomurica. Abdo- 

 men generally soft and spirally coiled in adapta- 

 tion to gastropod shells (abdomen secondarily 

 symmetrical in a few forms using other kinds of 



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