20 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 24 



Philippi (1860), Heller (1865), Cano (1889, as Porcellana mitra), 

 Meredith (1939), and Haig (1955). The color of preserved specimens 

 has usually been described as either pale violet, reddish, or brown, with 

 white stripe and darker marblings. Meredith's color illustration, made 

 by Anker Petersen from a freshly caught specimen, and reproduced 

 herein (see frontispiece), shows excellently both the natural color and 

 characteristic pattern. 



Ecology: The species has been taken in the littoral zone under 

 stones, and to a depth of about 7 fathoms. The Velero III dredged it 

 on two occasions at 5 fathoms, the substrate being rock in one case 

 and sand in the other. 



Bouvier (1906) reported young specimens taken at Valparaiso, 

 Chile, as commensals on a sea star, Asteracanthion helianthus [=Heli- 

 aster helianthus (Lamarck)]. Porter (1926) reported young specimens 

 between the bases of spines of a sea urchin, Loxechinus albus (Molina), 

 mentioning that they were found on many of these urchins at Val- 

 paraiso. Velero III collectors recovered a young specimen from a sea 

 star, Stichaster aurantiacus \_=S. striatus Miiller and Troschel] at 

 Bahia de la Independencia, Peru (Meredith, 1939). Haig (1955) re- 

 ported a specimen collected by Prof. Riveros-Zuniga at Montemar, 

 Chile, from a sea star, either Stichaster aurantiacus [ = 5. striatus] 

 or Meyenaster gelatinosus (Meyen). Haig (1955) also reported com- 

 mensal specimens in the Hamburg Museum collection, taken by R. 

 Paessler from a sea urchin at Mollendo, Peru, and from sea stars at 

 Caldera, Chile. Although Bouvier (1906) thought it probable that com- 

 mensalism in this species is confined to juveniles, the Mollendo and 

 Caldera specimens examined by the writer included large adults, some 

 of them ovigerous females. 



Ovigerous females have been collected in January, February, April, 

 and November. 



Remarks: The variation, with growth, in conformation of front and 

 number of carpal spines has resulted in the description of this species 

 under several names. Dana's type of Porcellana mitra had characters 

 typical of young specimens. Philippi described it as Porcellana spinosa 

 from a specimen with a tridentate front, but the number of carpal 

 spines was not specified. Cunningham described it from typical adult 

 examples as Porcellana patagonica, a name used (in the combination 

 Petrolisthes patagonicus) by several subsequent writers, who failed to 

 recognize its identity with Porcellana mitra and who may have been 



