£28 - 



Henarlcs .- Ivumeroiis individnals of this snail species are 

 present in both colleotions. On all except the most opaque shells, 

 faint, microscorjic concentric markings, due to differences in the 

 texture of the shell rather than to sculpture, are visible, and 

 on a few more or less translucent, polished valves thece markings 

 are quite distinct. Rg^diating lines on the auricles are seldom 

 observe*^ and when present thev are subordinate to the inoons-nicuous 

 concentric lines. ■: trie anterior auricle of the right valve the 

 concentric lines are most lorominent and are slightly roughened. 

 ^^ypicaX individuals are of the following dimensions: 



A right valve: lat. 5.9 mm.; alt., 5.7 mm.; length of hinge, 

 2.5 mm. 



A left valve: lat. 5.5 ram.; alt., 5.7; mm.; length of hin^'-e, 

 2.3 mm. 



The small, thin, smooth valves of this species, v:ith the mark- 

 ed proviuculum cannot be confused with any of the coexistent Pec- 

 tens. Pec ten ( O::olo-oe etenl oligolepis Brown and Pilsbry (1) from 

 Gatun is smaller, with a more roxmded outline and faint soul-oture. 



fl). Proc. Acad. Nat. 3c i., Philadel-nhia, vol. 64, ov. 512, 513, 

 text fig. 5, 1912. 



Ocourrenoe .- Upoer Oligocene: Oak Grove sand, I?lorida (Dall, 

 1398); Lower I.Iiocene: Bowden beds, Bowlen, ^am.aica (Dall, 



1898). Pliocene: Limon, Costa Pdca (^all, 1898). 



