NATURAL SCIENCES OP PHILADELPHIA. 91 



Merycodus, Tilanotherium, Leptochcerus, Hyracodon, Merychippus, Ischyromys, Pa- 

 loeolayus, Eumys, Deiniclis, and Leptarctus are peculiar, extinct, mammalian genera, 

 from the tertiary formations of Nebraska, -wliicb have heretofore been generally 

 viewed as belonging to the eocene period, but which from their affinities, 

 from the associated genera, and the absence of others so common in the 

 eocene deposits of Europe, I suspect rather to belong to the miocene period. 

 The first seven genera, above mentioned, are true ruminants, with the teeth con- 

 structed upon the same type as those of living ruminants ; — a type which is not 

 found in the tertiary deposits of Europe and Asia earlier than the miocene 

 period. 



EtUdodon, Paloeochcerus, Rhinoceros, Eipparion, Sieneofiber, AmpMcyon, and 

 Machairodus, are common to the Nebraska tertiary deposits and to the miocene 

 and later tertiary deposits of Europe ; and they have not been found in the 

 eocene formations of the latter continent. 



Of the genera Anchitherium, Hyopolamus, and Ilycenodon, species are found 

 common to the Nebraska tertiary deposits and the European eocene and miocene 

 deposits. 



Remains of Palceotherium, Anoplotherium, and Lophiodon, so common in the 

 eocene formations of Europe, are entirely absent from the Nebraska tertiary 

 formations. 



Titanoiherium of Nebraska most nearly approaches the miocene Chalicotherium 

 of Europe and Asia. 



The Nebraska rodents Ischyromys, PalcBolagus, and Eumys most closely ap- 

 proach the Arctomys, Lepus, and J/ms of European miocene and later deposits. 



Very numerous remains of Testudo are found in association with the Nebraska 

 tertiary mammals ; and extinct species of the same genus belong generally to 

 the miocene and later deposits of Europe. 



The remains of Mastodon and Camelops mentioned in the the list, I suspect to 

 belong to the post pliocene age of the upper Missouri country. 



Ischyr other ium appears to be an animal allied to the llanatus. Its remains are 

 stated by Dr. Hayden to have been obtained from a lignite bed (miocene*) near 

 Moreau and Grand rivers ; but I must leave it to this indefatigable explorer to 

 determine whether it belongs to the same age as the numerous extinct terres- 

 trial mammals of Nebraska. 



Thespcsius I suspect to be a huge dinosaurian. Its remains are stated to be- 

 long to the lowest member of the lignite formations (miocene) of Grand River. 



The species of Clupea was discovered by Dr. John Evans, in a tertiary deposit 

 on Green River, Missouri ; but the exact age of this formation I have no 

 means of determining. 



Investigation on the Rock Guano from the Islands of the Caribbean Sea. 



BY WM. J. TAYLOR. 



Though much has been written and published on the Columbian Guano of 

 the Caribbean Sea, which is also termed Phosphatic Guano, native Super- 

 Phosphate of Lime, &c., I have considered the subject not entirely exhausted, 

 and have for some time past been paying especial attention to its composition, 

 and have also endeavored to gather all possible information regarding its occur- 

 rence. To Dr. D. Luther, President of the Philadelphia Guano Company, I am 

 particularly indebted, for his kindness in furnishing me with material for the 

 investigation from the various groups of islands, and for information regarding 



* Proc. Acad. Nat. Sci. viii. 268. 

 1857.] 



