349 Costa Rica Miocene — Olsson 177 



Genus LliVIOPSIS Sassi 



LimopsiS monilis, n. sp. Plate 26, figures 23, 24 



Shell small, solid, moderately convex and subcircnlar in form 

 but slightly oblique; the hinge-line is straight, the anterior dor- 

 sal submargin very small, the posterior large undifferentiated 

 from the rest of the shell ; the umbos are high and prominent, 

 lying a little in front of the middle; exterior sculptured with 

 strong radial ribs which are largest and strongest on the middle 

 of the shell disk, finer on the dorsal submargins; these ribs are 

 crossed by high widel}^ spaced concentric lamellae, more closely 

 spaced on the umbos; the lamellse on crossing the ribs are raised 

 into short, spine-like fringes which are directed ventrally; inter- 

 ior of shell deep; the hinge-line with a small cartilage pit at the 

 anterior 1-3 of the shell; it is bordered on the anterior side by a 

 set of 3 high, projecting teeth and 4 on the posterior side, the 

 ventral and a part of the anterior margin is crenulated, most fine- 

 ly in the middle and quite coarsely at the posterior portion. 



Length 1.75, height 2.00, semidiameter .60 mm. 



This is a small, subcircular species with a crenulated inner 

 margin and a strong surface sculpture of ribs crossed b\' distant 

 concentric fringes. It is fairly common at its type localitj^, giv- 

 en below. 



Gatiin Stage: Old Man Sam Creek, i mile south of beach 



{A. C. Veatch, collector). 



Genus GLYCYMERIS, Da Costa 



Glycymeris canalis Brown and Pilsbry Plate i8, figures 2-7 



Glycymeris canalis Brown and Pilsbry, 191 1, Proc. Acad. Nat. Sci. 



Phila., vol. 63, p. 364, pi. 28, fig. 10. 

 Glycymeris trilobicostata Pilsbry and Brown, 1917, Proc. Acad, Nat. 



Sci. Phila. 



Very abundant locally in the Gatun beds of Costa Rica, are 

 small and medium sized Pectunculids belonging to the group of 



