NO. 8 HAIG: THE ATLANTIC GALATHEIDEA 27 



both the Galapagan and Caribbean specimens of P. marginatus examined 

 by the present writer. The Petrolisthes galathinus reported by Hult 

 (1938) from the Galapagos Islands is probably P. marginatus also. 



The following color notes were made from the Tobago Island 

 specimen by Mr. Anker Petersen, formerly staff artist of the Hancock 

 Foundation. Terminology is from Ridgway's "Color Standards and 

 Color Nomenclature" (1912): 



Carapace dull Van Dyke red. Antennae scarlet, passing into orange 

 towards tips. Ej^es reddish brown. Chelae same as carapace but lighter. 

 Tooth ridge of fingers white. Tips of fingers yellow orange. Merus and 

 carpus of walking legs same as carapace but darker. Propodus reddish 

 brown at base but gradually passing into bright scarlet. Dactyl pale 

 scarlet. Entire ventral side dull carmine. 



Petrolisthes vanderhorsti Schmitt 



Petrolisthes vanderhorsti Schmitt, 1924a, p. 73 (type locality, Caracas 



Bay, Curagao) ; 1936, p. 374. 

 Petrolisthes van der horsti Schmitt, 1924a, pi. 8, fig. 7. 



Previous records. — 

 Curasao: C. J. van der Horst (Schmitt, 1924a). Bonaire: P. Hummel- 

 inck (Schmitt, 1936). 



Material examined. — 

 A25-39. Isla Cubagua, Venezuela; Apr 14, 1939; shore. l?ov. 



Measurements. — The single specimen examined measured 5.6 mm. 



Remarks. — Petrolisthes vanderhorsti is known from the littoral, 

 from coral rock and anemones of the genus Macandra. 



Schmitt (1924a) mentioned the finely broken up lateral walls of the 

 carapace in this species and in P. nodosus, a character which apparently 

 has not been found in any other member of the genus Petrolisthes. 

 Among 31 species of Petrolisthes from the east and west American 

 coasts examined by the writer, only four, including P. vanderhorsti and 

 P. nodosus, had five plates in the telson of the abdomen. The combina- 

 tion of five-plated telson, finely divided lateral walls, and tridentate 

 front might serve to set P. vanderhorsti and P. nodosus apart as a dis- 

 tinct genus or subgenus, should Petrolisthes be subdivided. 



Petrolisthes nodosus Streets 



Petrolisthes nodosus Streets, 1872, p. 133 (type locality. Saint Martin 

 Island). Benedict, 1901, p. 134. Schmitt, 1924a, p. 73, pi. 8, 



fig. 8. 

 Petrolisthes (Pisisoma) nodosus Ortmann, 1897, pp. 295, 296. 



