4^5 



Costa Rica Miocene — Olsson 243 



normal, the left valve with 3, narrow; cardinal teeth and a wide 

 ligament. 



Height 39, length 38 ? diameter 5 mm left valve. 



Represented by a single, imperfect specimen from the Gatun 

 of Rio Betey. It is but slightly convex, and in form approach- 

 es very closel}^ a species in the Newcomb collection from the 

 Bay of Fonseca, which is probably the C. Kroyeri Philippi. The 

 fossil shell is more perfectly circular in form. 



Gatun Stage: Rio Betey. 



Cyclinella subquadrata Hanley, var. quitana, n. sp. Plate 31, fig. 8 



Shell small, thin, convex and subcircular in form; beaks 

 small but distinct, with inflated umbo and small beak situated 

 at the anterior Yi ; the anterior end is narrow and slightly pro- 

 duced, while the posterior end is wide and with the hinge-margin 

 is subquadrate in form; the surface is sculptured with fine, ir- 

 regular, concentric growth-lines, which are strongest and more 

 regular on the posterior dorsal submargin; the interior is con- 

 cealed. 



Height 28, length 31, diameter of the right valve 7 mm. 



This is a smaller and more convex species than the beteyeyi- 

 sis and like that species, it seems to find its recent analogue on 

 the Pacific side, in this case the C. s^lbquadrata Hanley. On the 

 Pearl Islands in the Bay of Panama I collected a few small 

 valves which are probably the C. subquadrata Hanley, but they 

 are not so produced anteriorly as is shown in Reeve's figure. 

 These Pearl Island shells are very similiar to the Costa Rican 

 fossil, differing mainly in their more inflated umbos and in 

 slight difference in form. 



From the Gatun beds of the Canal Zone, Dall has described 

 C. gatuneyisis, but that species is very distinct from the two 

 Costa Rican Cyclinellas. 



Gatun Stage; Quitana creek. 



