Amazonian Fossils. 



561 



the lignite band, beginning about twenty feet from the 

 surface. They are best exposed about two miles below 

 the town. A well dug at Iquitos shows, first, seven feet of 

 variegated clays, nine feet of fine sand ; next, several feet 

 of pebbles; and then, blue clay containing shells. From 

 the collections made at these localities, the following 

 thirty species have been determined : 



Bivalves. 

 Pachydon carinatus, Conrad. 



" obliquus, Gabb. 



" <enats,Gabb. 



" erectus, Conrad. 



" cuneatiis, Conrad. 



" ovatus, Conrad. 



" cuneiformis, Conrad. 



" dispar, Conrad. 

 Dresseina scrijita, Conrad. 

 Anodon Batesii, Woodward. 



" Pebasana, Conrad. 

 Triquetra longula, Conrad. 

 Ostomya papyria, Conrad. 

 Haplothaerus capax, Conrad. 



Univalves. 

 Isaea Ortoni, Gabb. 



" lintea, Conrad. 

 Liris laqueata, Conrad. 

 Ehora crassilabra, Conrad. 

 Nesis bella, Conrad. 

 Neritina Ortoni, Conrad. 

 Dyris gracilis, Conrad. 

 Hemisinus sulcatus, Conrad. 

 " Steerei, Conrad. 



Iquitosa tuberculifera, Conrad.* 

 Pachytoma tertiana, Conrad. 

 Toxosoma eborea, Conrad. 

 Cirrobasis venusta, Conrad. 

 Liosoma curta, Conrad. 

 Cyclocheila Pebasana, Conrad. 

 Bulimus lintetis, Conrad. 



These interesting fossils have attracted much attention 

 by their extraordinary character, and by the light which 

 they throw upon the largest continuous Tertiary formation 

 in the world. All the species and twelve of the genera 

 are extinct. The impalpable clay in which they were im- 

 bedded was admirably fitted for their preservation. Some 



Iquitos, where I found shells even more abundant than below. All the known 

 localities were discovered by myself, and by Mr. Hauxwell, under my instruc- 

 tions. 



* This beautiful and characteristic shell was originally described in Proceed. 

 Acad. Nat. Sci. Phil., vol. xxvi., as a Hemisinus ; but Mr. Conrad has since 

 decided that it belongs to a new genus, distinguished by its high, Melania- 

 like spine and short, patulous aperture. "Subulate, subturreted, whorls nu- 

 merous, spirally ribbed ; aperture short, oval ; columella regularly arched, 

 solid, subtruncated at base; outer lip regularly curved." The name is de- 

 rived from Iquitos, Peru, where it is very abundant. Hemisinus and Trique- 

 tra are characteristic genera of South American rivers. 



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