206 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 20 



Re/narks: One V-shaped groove circumscribes the ligamental area. On 

 larger specimens a second groove may be developed, though it does not 

 become definitely V-shaped. The ligamental area is crossed by elastic 

 bands which are usually worn off in the middle part. If a second groove 

 is developed, a secondary layer of elastic bands will also be present. In 

 small specimens, the ligament is posterior to the umbones only. The 

 anterior groove grows rapidly, however, and finally the umbones are 

 only slightly anterior to the center of the ligamental area. The perio- 

 stracum is bristly in the interspaces, the bristles becoming long and thin 

 on the posterior slope. The mantle margin is unpigmented. The ab- 

 dominal sense organs are similar to those of Anadara (Cunearca) chem- 

 nitzi and Anadara {Cunearca) perlabiata (Heath, 1941, PI. 15, fig. 11; 

 PI. 14, fig. 6), with a trilobate flap above the anal opening. A papilla 

 in the opening is sometimes visible. 



Anadara {Cunearca) nux may attain a length of 25 mm (Maury, 

 1922). 



Occurrence: Dredged from 2 to 40 fms. The larger part of the material 

 at hand taken between 10 and 20 fms. Lives in bottom of fine sand or 

 mud. 



Distribution: Bahia Concepcion, east coast of Baja California (Hertlein 

 and Strong, 1943) to Negritos, Peru (Olsson, 1924). 



Anadara (Cunearca) aequatorialis (Orbigny) 1846 

 PI. 15, figs. 27 a-c; text-figs. 92 a-c 



Area aequatorialis Orbigny, Voyage dans I'Amerique Meridionale, vol. 

 5, pt. 3, p. 636 ; new name for Area ovata Reeve 1844, not Area ovata 

 Gmelin in Linne 1791; not Area ovata Buckman in Murchison 

 1844. 



Syn.: Area suhelongata Nyst 1848, new name for Area ovata Reeve. 



Type loc: Santa Elena, Ecuador; 6 to 8 fms ; sandy mud. 



Holotype: British Museum? 



Occurrence: In fine sand or mud, from 7 to 40 fms. 



Distribution: Mazatlan, Mexico, to Zorritos, Peru. The Galapagos 



Islands. (Hertlein and Strong, 1943). 



Fig. 90. Anadara {Scapharca) ohesa (Sowerby) 1833, Off San 

 Jose, Guatemala, a. Lateral view. b. Dorsal view. c. Ab- 

 dominal sense organs. Length, 25.7 mm. 



Fig. 91. A. {Cunearca) nux (Sowerby) 1833. Off San Jose, Guate- 

 mala, a. Lateral view. b. Dorsal view. c. Abdominal sense 

 organs. Length, 15.5 mm. 



Fig. 9'2. A. {Cunearca) aequatorialis (Orbigny) 1846. Off San Jose 

 Guatemala, a. Lateral view. b. Dorsal view. c. Abdominal 

 sense organs. Length, 14 mm. 



