DECAPODA 399 



Division 3. CATOMETOPA.* 



Carapace more or less rectangular, with a wide, straight ante- 

 rior margin and a straight but narrower hinder margin; no rostrum pres- 

 ent: 4 families, including the land and strand crabs, whi'ch are among 

 the most active and intelligent crabs. 



Key to the families of Catometopa here described: 



Oi Carapace soft and membranous; in oyster or mussel shells. 1. Pinnotheridae 

 fl2 Carapace hard and firm 2. Ocypodidae 



Family 1. PINNOTHERIDAE. 



Carapace nearly circular and more or less membranous; eye stalks 

 veiy small: small crabs, the females of which live in the mantle cavity 

 of certain pelecypods or in annelid tubes, the males being 

 free-swimming; 1 genus. 



Pinnotheres Latreille. With the characters of the 

 family: several species. 



P. ostreum Say. Oyster crab. Surface of body 

 smooth and shiny; length and breadth of carapace about 

 5 mm.: in the mantle cavity of the oyster. 



P. maculatus Say. Mussel crab (Fig. 637). Surface hairy; length 

 and breadth about 8 mm. : in the mantle cavity of Mytilus edidis and other 

 bivalves, from Cape Cod to South Carolina. 



Family 2. OCYPODIDAE. 



Carapace broad anteriorly and more or less quadrangular; eye stalks 

 long, each lying in an elongated groove-like orbit : 6 American genera. 



1. OcYPODEf Fabricius. Carapace square in shape, with distinct 

 lateral margins ; chelipeds small, somewhat unequal ; other periopods flat, 

 with pointed tips; eye stalks stout: 1 American species. 



0. albicanst Bosc {0. arenaria Say). Sand crab. Length of carapace 

 30 mm. ; breadth 35 mm. ; chelipeds of nearly the same size in both sexes ; 

 claw with serrated margins : New Jersey to Florida and southw^ards, living 

 in deep burrows above high-water mark; a very active crab which has 

 become a terrestrial animal. 



2. UCA§ Leach {Gelasimus Latreille). Fiddler crabs. Chelipeds of 

 male of very unequal size, one, usually the right, being enormously devel- 



* See "The Catometopous or Grapsoid Crabs of North America," by Mary J. 

 Rathbun, Am. Nat., Vol. 34, p. 583, 1900. 



t See "Carciuological Notes, No. Ill, Revision of the Genus Ocypoda," by J. S. 

 Kingsley, Proc. Acad. Nat. Sci., Phil., for 18S0, p. 179. 



t See "Habits, Reactions, and Associations in Ocijpoda arenaria/' by R. P. 

 Cowles, Monograph No. 103, Carn. Inst, of Wash., 1908. 



§ See "Carcinological Notes, No. 11, Revision of the Gelasimi," by J. S. Kingsley, 

 Proc. Acad. Nat. Sci., Phila., for 1880, p. 135. 



