190 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 20 



The teeth are very distinctly transversely striated, often somewhat 

 irregularly. Acar gradate has tiny black pigmented eye-spots along the 

 whole mantle margin except for the foot-aperture part. 



It has been discussed whether Acar gradata ought to be considered 

 conspecific with the West Indian Acar doTningensis (Lamarck) == 

 reticulata Dall 1898, non Gmelin (see Reinhart, 1939, pp. 42-43). 

 Heath (1941) found several distinguishing characters in the anatomy 

 of the two species. 



Occurrence: Intertidal on rocky shores. Occasionally taken down to 20 

 fms. 



Distribution: Laguna de Scammon, west coast of Baja California, the 

 Gulf of California, to Negritos, Peru (the Peru locality reported by 

 Olsson, 1924). The Galapagos Islands. 



Acar bailyi Bartsch 1931 

 PI. 12, figs. 14, 15 a-e 



Acar bailyi Bartsch, Proc. U. S. Natl. Mus., vol. 80, art. 9, 1931, p. 2. 

 Syn.: Acar gradata auct. non Broderip and Sowerby 1829. 

 Arcopsis solida auct. non Sowerby 1833. 

 Acar pernoides Strong 1932 (perhaps not Carpenter 1856). 

 Fig.: Bartsch, 1931, PI. 1, five middle figures; Reinhart, 1939, PI. 3, 



figs. 3 a-d. 

 Anatomy: Heath, 1941 {Barbatia {Acar) pernoides). 

 Type loc: Balboa, (near San Diego), California; under stones. 

 Holotype: U. S. National Museum no. 382474. 



Remarks: There has been much discussion about the correct name for 

 this species (see Strong, 1932, and Reinhart, 1943, pp. 35-36, 82). 

 Carpenter (1856b) described Byssoarca pernoides from San Diego from 

 a single valve with a length of about 17 mm, but the description is not 

 sufficient to allow a recognition of the species and it has been impossible 

 to locate the type, which is supposed to be in the Gould collection. Until 

 the type specimen is examined, it is best not to use the name pernoides. 

 The figure of the holotype of Acar bailyi Bartsch shows a shell with 

 slightly fainter radial sculpture on the middle of the disc, resembling the 

 southern species Acar pusilla (Sowerby). This character seems to be 

 typical for specimens from southern California. 



Many samples from the Gulf of California down to Panama and the 

 Galapagos Islands are here referred to Acar bailyi, but they are slightly 

 larger and more even in sculpture. They have probably been recorded 

 earlier as Arcopsis solida or Acar gradata from these more southern 



