NO. 2 ROST: THE FAMILY ARCIDAE 205 



irregular band on the side that touches the shell. No eye-spots can be 

 distinguished with certainty. Maury (1922) reports a specimen with a 

 length of 48 mm. This species should perhaps be referred to the subgenus 

 Cam Gray. 



Occurrence: This species is recorded from 3 to 13 fms. It is dredged 

 from sand, sandy mud, and rocky bottom. Carpenter (1856a) reports 

 young specimens on Spondylus and adults on Murex. It is known to 

 occur from the Gulf of California to Atacames, Ecuador. Hertlein and 

 Strong (1943) say it occurs in the Pleistocene in Magdalena Bay, 

 Lower California. Four living specimens from Bahia de la Magdalena 

 are present in this material. 



Distribution: Bahia de la Magdalena, Baja California, and Gulf of 

 California, to Payta, Peru (reported by Olsson, 1924). 



Anadara (Scapharca) obesa (Sowerby) 1833 

 PI. 16, figs. 28 a-b ; text-figs. 90 a-c 



Area obesa Sowerby, Proc. Zool. Soc. London, 1833, p. 21. 

 Type he: Atacames, Ecuador; 7 fms. 

 Holotype: British Museum? 



Remarks: This species can scarcely be confused with other west Ameri- 

 can Anadaras because of its great number of ribs (39 to 44). It attains 

 a length of 40 mm (Maury, 1922). As shown on text-fig. 90 c, the 

 abdominal sense organs of this species are of the same type as those of 

 Anadara (Cunearca) nux (Sowerby) and Anadara (Cunearca) aequa- 

 torialis (Orbigny). 



Occurrence: Not common. Taken in fine sand or mud from 12 to 61 

 fms. 



Distribution: Off San Jose del Cabo, south coast of Baja California, to 

 Negritos, Peru (Hertlein and Strong, 1943). 



Subgenus CUNEARCA Dall 1898 



Cunearca Dall, Trans. Wagner Free Inst. Sci., vol. 3, part 4, 1898, 



p. 618. 

 Type of subgenus: Area incongrua Say 1822 (orig,). 



Anadara (Cunearca) nux (Sowerby) 1833 

 PI. 16, figs. 29 a-c; text-ngs. 91 a-c 



Area nux Sowerby, Proc. Zool. Soc. London, 1833, p. 19. 

 Type loc: Jipijapa, Ecuador; 12 fms; sandy mud. 

 Holotype: British Museum? 



