180 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 20 



Occurrence: Living specimens were dredged between 2 and 50 fms. 

 The bottom usually consisted of sand, shells, and rocks, and the speci- 

 mens were attached to rocks, shells, corals, or to each other. 

 Distribution: Laguna de Scammon, Baja California, and the Gulf of 

 California, to Payta, Peru. Also found in the Galapagos Islands, accord- 

 ing to Hertlein and Strong (1943). 



Area (Area) mutabilis (Sowerby) 1833 

 PI. 11, figs. 1-2; text-figs. 79, 80 a-c 



Byssoarca mutabilis Sowerby, Proc. Zool. Soc. London, 1833, p. 17. 



Fig.: Reinhart, 1943, PI. 11, figs. 8-10. 



Type loc. : Isla La Plata, Ecuador ; under stones. 



Holotype: British Museum? 



Remarks: Two specimens are figured to show the variation of the liga- 



mental area (PI. 11, figs. 1-2). Text-fig. 79 shows the arrangement of 



the periostracum in a beautifully preserved specimen. The periostracum 



is yellowish-brown, foliaceous and serrated ; it is usually better developed 



on the umbonal keel and is not so easily worn off on this part of the 



shell. 



Eye-spots are present around the whole mantle margin. They are 

 rather large posteriorly, and very small elsewhere. 



The largest specimen in the collection, obtained by shore collecting 

 in the Gulf of California, has a length of 41.2 mm. Other measurements 

 would not be accurate, as the specimen is very eroded. 

 Occurrence: The common habitat for this species is under rocks at low 

 tide, but it is occasionally dredged down to 45 fms (reported by Hert- 

 lein and Strong, 1943). One sample in the material at hand contains 14 

 specimens from the Galapagos Islands. They are typical Area mutabilis 

 and not Area ventricosa Lamarck 1819 {= triincata (Sowerby) 1833), 

 which has been reported from the Galapagos Islands. 

 Distribution: Bahia de la Magdalena, west coast of Baja California, 

 and the Gulf of California to Ecuador (Hertlein and Strong, 1943). 

 Galapagos Islands. In the Pleistocene of Ventura County, California 

 (Reinhart, 1943). 



Genus BARB ATI A Gray 1842 



Barbatia Gray, Synopsis of the Contents of the British Museum, ed. 44, 



1842, p. 81. 

 Type of genus: Area barbata Linne 1758. (Subsequent designation by 



Gray, 1847, p. 197). 



