- 199 



Renarks .- The almost smooth, very convex right valves and 

 moderately concave, relatively strono-ly sculptured left valves of 

 this species are conspicuous among the 3owden scallops. The rihs 

 on young left valves are weaker and iiarrovier than on adults. 



P. "bovrdenensis is closely related to the recent ]^, ziczao 

 Linnaeiis (1), hut the riprht valve of the recent form is not q^^ite 

 as convex and the left valve is s';ulptured vjith more numerous rihs, 

 separated hy narrow impressed lines. P. medius Lamarck (?) is 



(1). Syst. i-at., ed. 10, p. 695, 1753; Heeve, Conch. Icon, 

 vol. 8, Pecten . pi. 6. fig. 29, 1852. 



more strongly rihhed. The Oosta xiican Pliocene P. limonensis 

 Dall (5) is smaller, ~:ith less poorly defined rihs on hoth valves, 



(2). Anim. sans Yert,, vol. 6, p. 16,?, 1819; Ohemjiits, Jonch. 

 Oah., vol. 7, pi. 60, figs. 585, 587, 589, 1784. 



(5). loc. Git., p. 717., 1898, ( = Janira laevi-^ata Gabb. Jour. 

 Acad. Kat. Sci., Philadelphia, 2nd ser., vol. 0, p. 579 

 pi. 47, fie-. 84, 1881, not P. laevi^atus Goldfxiss, 18?5) 



Trie left valves which Bttse described from the '^liocene of 

 Tttxteoec, I'exico may be bowdenensis . biit the interspaces seem to 



be too flat and deep for that species. 



OGCu,rrence .- Louer I.Iiocene: Bowden beds, 3ov/den, Jamaica 

 (Dall, 1898). Pliocene.- Tuxteoec, T'exico (39.se, 1905, 3 906). 



