DECAPOD CRUSTACEANS OF THE WEST INDIES 121 



Family Porcellanidae 

 Genus Petrolisthes 



34. Petrolisthes quadratus Benedict 



Figures 32, 34a 



Petrolisthes quadratus Benedict, 1901, p. 134, pi. 3: fig. 4 [type-locality: reefs at 

 Ponce, Puerto Rico]. — Haig, 1956, p. 18. 



Diagnosis. — Carapace broader than long, smooth (not rugose), 

 lateral wall entire (not formed of two or more pieces separated by 

 membranous interspaces). Front broadly triangular, without lobiform 

 teeth at inner angles of orbit. Movable portion of antennal peduncle 

 not excluded from orbit. Chelipeds of adidt male similar, slightly 

 unequal, depressed, smooth; carpus with flexor margin entu'e (not 

 lobate or dentate), distal extremity of extensor margin blunt, not 

 spinose. A small species, maximum carapace length in midline about 

 8 mm. 



Color in life. — Carapace tan with greenish-brown anterior and 

 lateral areas; greenish color extending from anterior border postero- 

 mesially along postorbital grooves to level of base of cheliped; pair 

 of light tan spots between inner pair of postorbital grooves. Lateral 

 wall of carapace with long upper and short lower triangular areas 

 of olive brown. Abdomen tan with very narrow brownish band on 

 posterior margin of each somite. 



Second segment of antennal peduncle olive brown above fading 

 to tan below; flagellum tan with distal margin of each unit olive 

 brown. Third maxilliped with extensor margins of podomeres olive 

 brown, remaining surface cream with tan mottling; merus with 

 extensor margin olive brown and remaining surface pale tan with 

 greenish splotches; carpus olive brown; propodus and dactyl pinkish 

 tan on flexor portions, greenish brown on extensor portions. Chela 

 of first pereiopod olive brown above with opposable margin of fixed 

 finger cream, distal portion of extensor margin of dactyl and lower 

 surface tan; merus and carpus olive brown above, tan below. Second 

 through fourth pereiopods having merus tan with olive-brown extensor 

 and flexor margins; carpus tan with longitudinal olive-brown stripes; 

 propodus with two transverse bands; and dactyl with triangular 

 mark proximally. Lower surfaces of remaining pereiopods, and all of 

 fifth, cream to pinkish tan. 



Material examined. — The material of Petrolisthes quadratus 

 collected on Dominica at station 110 consists of 62 males (carapace 

 lengths 2.2-5.1 mm), 44 females (cl 2.1-4.2 mm), including 34 with 

 eggs (cl 2.7^.2 mm), and 1 juvenile (cl 1.2 mm). 



