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, which are among 

 the most active and intelligent crabs. 



Key to the families of Catometopa here described: 



! Carapace soft and membranous; in oyster or mussel shells. 1. PINNOTHERIDAE 

 3 Carapace hard and firm 2. OCYPODIDAE 



FAMILY 1. PINNOTHEBIDAE. 



Carapace nearly circular and more or less membranous; eye stalks 

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

 of certain pelecypods or in annelid tubes, the males being 

 f ree- 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 edulis 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 southwards, 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 '.'Carcinological Notes, No. Ill, Revision of the Genus Ocypoda," by J. S. 

 Kingsley, Proc. Acad. Nat. Sci., Phil., for 1880, p. 179. 



t See "Habits, Reactions, and Associations in Ocypoda arenaria," by R. P. 

 Cowles, Monograph No. 103, Cam. 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. 



