i8o Bulletin 39 353 



All our specimens were collected in the lower Gatun of E. 

 Grape Pt., Cliff Creek in Eastern Costa Rica, the largest shell 

 measuring as follows; 



Height 56, length 55, diameter of both valves 32 mm. 



Gatun Stage: Coll. ^, East Grape Point. 



Glycymeris castaneus Lamarck Plate 18, figures 13, 14 



Pediinculus castaneus Lamarck, 1819, Anim. sans Vert., voL 6, p 

 53- 



Pedimculus casta^ieus Reeve, 1843, Conch. Icon., Pedunculus pL 6, 

 fig- 32. 



Our collection from the Banana River contains several small 

 Pectunculids which differ from the jamaicensis and its allies by 

 their less circular shell, greater convexity and coarser radial 

 sculpture. These shells agree however very closely with a recent 

 species which is abundant on the beaches of northern Costa 

 Rica, which appears to be the Glycyjneris castaneus of Lamarck. 

 Glycymeris castaneus is distinct from undutus Linne (6^. lineatus 

 Reeve) with which it is sometimes united, differing by its form 

 which is more produced posteriorly but not angulated and by its 

 more pronounced radial costse. Both species are similiarly col- 

 ored with chestnut markings. 



Gatun Stage: Hill No. j, Banana River. 

 Quitana creek. 



Glycymeris decussatus Linnseus Plate 19, figures 6, 7 



Area decussatus Linnaeus, 1758, Syst. Nat., ed. 10, p. 694. 

 Pedunculus pennacea Lamarck, 1819, An. s. Vert., vol, 6, p. 51. 

 Pedunculus pennacea Reeve, 1843, Conch. Icon., Pedunculus, pi. 

 5, fig- 24. 



Pedunculus decussatus Linne. P. pennaceus Lamarck, (Lamy) 191 1, 

 Journ. de Conchy., vol. 59, p. 119, pi. 3, fig. 7. 



Of this rare shell, more commonly known as the G. penna- 

 cea Lamarck we have several excellent specimens collected by 



