348 DESCRIPTIONS OF CARIBBEAN MIOCENE FOSSILS. 



I have named this beautiful shell after my "guide, councillor, and friend," 

 John H. Lyon, of Sipurio, Talamanca, without whose constant aid the expedition 

 would have been a failure. 



LIMA, Brug. 

 L. PAPYRACEA, Gabb, n. s., PL 45, fig. 26. 



Shell moderate in size, very thin, oblique, anterior margin very convex, pos- 

 terior nearly straight. Ears small, hinge straight and rather short, beaks promi- 

 nent and well curved inwards and forwards. The anterior surface — nearly half 

 the width of the shell — is perfectly plain, as is also a narrow space bordering the 

 posterior margin. The remainder, just about one-half of the area, carries about a 

 dozen small, regular, thread-like, radiating ribs. (One specimen before me counts 

 eleven, another fourteen.) 



Figure. About natural size. 



Locality. Sapote, Costa Rica. 



OSTRBA, Linn. 

 O. Tryoni, Gabb, n. s., PI. 45, fig. 21. 



Shell sub-rotund in outline, very convex, tri-plicate, the plicse noduled where 

 crossed by the growth lines. Very much thickened, slightly winged. 



The figure is two- thirds the natural size. 



Locality. Sapote, Costa Rica. 



SCHIZASTER. 

 S. ScHERZERi, Gabb, n. s., PL 45, fig. 28, 28a, 28b. 



Shell moderately large, high ; most elevated posteriorly, in a crest between the 

 two posterior ambulacral grooves. Sides pretty regularly convex, tapering more 

 rapidly behind ; posterior end high and abruptly truncated, anterior end sloping. 

 Ambulacral grooves profound. Mouth broad, bordered by a strongly elevated lip 

 on its posterior margin. Anal aperture small. The spinous tubercles small above, 

 much larger on the under surface. 



Figures. Natural size. 



Discovered first by Mr. A. Scherzer, engineer in charge of the Eastern division 

 of the Costa Rica Railroad, above Paquare, on the Reventazon river. Afterwards 

 found at Sapote. 



