- ri7 - 



Gatun, which is larger, "-ith subeoual raiial striae on the ribs 

 and interspaces and the srxrface less ohviously scabrous; and 

 03cyg-omiFi optimum (1) , from the Oosta ^.ioan Miocene and Antigua (2), 



(1). idem, pp. 511-512, pi. 24, fig. 2 (- P. paranensis Cabb, 

 Jour. Aoad. ITat. S^i., ""hiladelphia, r'nd ser., vol. 8, n. 

 347, pi. 45, fi??. 24, 1881, non d'Orbigny). The Antic-uan 

 form V7hieh Dall (loc. cit., pp. 717-718, pi. 29, fig. 5, 1"^98) 

 described as P. gabbi , as a new name for Gab'^i's P. 'oaranensis . 

 is distinct; Gabb ' s spe c inens came from Sapote, Oosta ?.ica, 

 not Santo Domingo. 



(2). Brovm, A. P., Proc. Acad. Hat. Sci., Philadelphia, vol. 65, 

 pp. 501-602, 191.-^. 



which also is larger, more inequilateral, with the dorsnl half of 

 the ribs subrounded, the ventral half -reeled, radial striae on 

 the ribs and interspaces crossed bj' irregular inerementals, the 

 surface roughened, but not scabrous, the submargins foiraing a 

 high, steep ledge. 



Sowerbjy's failure to orovide figures for his three briefly 

 described Santo Domine-ian Pectens (25) has caused some confusion. 



i^)t Sovverby, G. B., Quart. Jour. Geol. 3oc. London, vol. 5, 

 p. 52, 1850. 



It is- surprising that Gabb shoixld have identified the present form 

 as oxygonus Sowerby since it obvioiisly conflicts with Sowprby's 



