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 Ivamarck Plate 18, figures 13, 14 



Pedunculus castaneus Ivamarck, 1819, Anim. sans Vert., vol. 6, p 



53- 

 Pedunculus castaneus Reeve, 1843, Conch. Icon., Pedunculus pi. 6, 



fig- 32. 



Our collection from the Banana River contains several small 

 Pectunculids which differ from the janiaicensis 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 Glycyineris castaneus of Lamarck. 

 Glycymeris castaneus is distinct from undutus Linne (G. lineatzis 

 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 costae. 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 Ivinnaeus, 1758, Syst. Nat., ed. 10, p. 694. 

 Pedunculus pennacea Lamarck, 18 19, 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. pe?i7ia- 

 cea Eamarck we have several excellent specimens collected by 



