82 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 23 



Chlamys patagonica (King). Bavay, 1936, p. 307. 



Holotype: ? 



Type locality : Strait of Magellan. 



Original description: P. testa sub-aequivalvi, brunnea, longitudi- 

 naliter creberrime elevato-radiata ; intus albida, longitudinaliter sub- 

 radiata ; long. 2% ; lat. 2% ; poll. 



Obs. auribus inaequalibus. 



Additional description: Shell averaging 55 mm in height and 

 length; left valve moderately convex, right valve less; hinge line varying 

 from slightly less than ^ to slightly more than ^ length of disk. Right 

 valve having from 23 to 28 low, broad, rather flat and often dichotomous 

 ribs, covered with fine concentric growth striae; ribs parallel to sub- 

 margins smaller; interspaces narrower than ribs, concentrically lamel- 

 lated and occasionally with low central riblets ; anterior auricle of moder- 

 ate length, with very fine concentric striae and 5 or 6 radiating riblets; 

 byssal notch shallow and ctenolium of 4 to 6 teeth; posterior auricle 

 about half as long and margin oblique, with fine concentric striae and 

 6 to 8 thin, oblique riblets. Left valve with higher and narrower rounded 

 ribs, often flanked by secondary ribs near ventral margin; interspaces 

 wider than ribs, having concentric ridges and a low central riblet; 

 anterior auricle same length as that of right valve, with vertical margin, 

 no byssal sinus, fine concentric striae and 7 or 8 small radiating riblets; 

 posterior auricle same as that of right valve. Color range small: left 

 valve white, with ribs and riblets of disk and auricles either brown, red- 

 brown or red; right valve paler than left or uncolored, but often pale 

 red on umbo. 



Remarks: This species is similar to the North American Chlamys 

 rubida in general appearance, but dififers in length of hinge line, rib 

 structure, sculpture and coloring. 



Geographical range: Eastern Pacific from Puerto Montt, Chile, to 

 Strait of Magellan ; western Atlantic from Puerto Quequen, Chubut 

 Territory, Argentina, to Strait of Magellan ; Falkland Islands. A single 

 juvenile right valve in the author's collection was found by a native on 

 the beach at Anakena, Easter Island ; it is quite worn, however, and 

 cannot be accepted as conclusive evidence that Chlamys patagonica 

 actually lives in that area. 



Geochronological range: Bavay referred vaguely to fossil records, 

 but the author could not locate confirming data. Available records indi- 

 cate this is a Recent species. 



