hill: geology of THE ISTHMUS OF PANAMA. 273 



C. Vamos d Vamos or Gatun Beds. 



Species were described from these beds by Conrad many years ago, 

 and later by myself. They have a rich fauna, but the fossils are all 

 pseudomorphs in calcite, in a tough matrix, and difficult to extract in 

 good condition. They contain a number of what have hitherto been 

 regarded as typical Claibornian species, some of which are common 

 to the Upper Tejon of California. Notwithstanding the fact, if it be a 

 fact, that they are found above the Orbitoides bed (B), which has a 

 distinctly Oligocene facies, I am obliged to regard them as Eocene. If 

 it were not for this stratigraphic puzzle I should refer them to the 

 Claibornian without hesitation. The species common to the Claiborne 

 sands are as follows : Lapia perovata Conr., Solarium alveatum Conr. 

 Natica (Lunatia) eminula Conr., a small Sigaretus or Naticina, Neverita 

 sp., and Cerithiopsis sp. Solarium alveatum and Xatica eminula, with 

 Turritella gatunensis (+ uvasana Conr.), and the genus Glyptostyla, 

 are also common to the Upper Tejon of California. A careful study of 

 the Gatun fauna might reveal other common species of Claiborne origin. 



The following genera were noted in the Gatun shale on a rapid ex- 

 amination of your material : Atys, Cylichna, Conus (2 sp., not Oligo- 

 cene), Glyptostyla (panamaensis Dall), Phos, Xassa, Xeverita (gibbosa 

 Lea), Lunatia (eminula Conr.), Xatica (sp.), Ampullina, Lupia (pero- 

 vata Conr.), Turritella (gatunensis Conr.), Solarium (alveatum Conr.), 

 Oniscia, Galerus, Trochita, Capulus, Xiso, Scala, Phasiauella (small 

 sp.), and two species of Dentalium. Among Pelecypods we find : 

 Xucula (large sp.), Leda (like acuta), Adrana, Area, Pecten (like 

 Poulsoni), Lucina (like crenulata), Diplodonta, Loripes, Chama, Car- 

 dium (haitensis), Cardium (large sp. like muricatum), Cardita (like a 

 small Claiborne sp.), Venus (mactropsis Conr.), Venus (wallii Guppy), 

 Dosinia, Tivela, Cytherea (dariena Conr.'?), Cytherea (sp.), Clementia, 

 Lucinopsis, Mactra, Solen, Tellina (dariena Conr.), Tellina (sp.), 

 Semele, Lyonsia, Corbula (3 sp.), and a Thracia, like undulata, but 

 distinct. The assemblage might live in 10-30 fathoms. 



D. Mindi Hill Greensand. 



The species in this material, without exception, have a deep water 

 facies and are such as we might expect to find in 50-200 fathoms, or 

 even more. The following genera are represented : Cylichna, Pleuro- 

 toma, Astyris, Turritella, Cerithiopsis, Solarium (alveatum Conr.), 



