THE CRUSTACEA OF NEW JERSEY. 369 



asymmetrical, either coiled to fit spire of dead mollusk shell that 

 animal usually inhabits, or bent, only occasionally well calcified, 

 symmetrical and straight. Caudal swimmerets present, narrow 

 and falcate usually. First three pairs of thoracic legs well de- 

 veloped, first pair massive and chelate, and second and third pairs 

 long, stout, monodactylous. Fourth and fifth pairs of thoracic 

 legs, one or both of which may be chelate or subchelate, exceed- 

 ingly short. Paired appendages may be present on first and 

 second abdominal somites of male and on first somite of female, 

 but on third to fifth somites of male and second to fifth of female 

 appendages usually developed on one side only. 



While these crabs are familiar to all visitors, or others at the 

 seashore, between the tides and along the sea beaches, they also 

 occur in very deep water, and have been taken in depths of over 

 two thousand fathoms. Several families are known, though only 

 one in our region. 



Family PAGURID^. 



The Hermit Crabs. 



Carapace usually somewhat elongate, somewhat broadened 

 posteriorly and feebly calcified laterally. Rostrum sometimes 

 fairly prominent, sometimes obsolescent and leaving ophthalmic 

 segment exposed. Thoracic sterna variable in breadth. Abdo- 

 men generally soft and spirally coiled in adaptation to form of 

 cast-off gastropod shell which animal generally uses as a habita- 

 tion. In few abnormal forms not using shell abdomen may re- 

 acquire secondary symmetry. Ophthalmic scales and antennal 

 acicle present and often large. Antennular peduncle usually of 

 moderate length and flagella usually short. Chelipeds usually 

 massive, equal and similar, or very unequal and dissimilar. Legs 

 of second and third pairs elongate, those of fourth and fifth pairs 

 short, fourth pair simple, subcheliform or cheliform, and fifth 

 pair subcheliform or cheliform. Abdominal appendages never 

 all bearing paired appendages. Usually appendages on left side 

 only, present on somites two to five or three to five. Occasionally 



24 MU 



