NOVKMBKE 23, 1900.] 



SCIENCE. 



809 



there is no evidence that any part of Central 

 America which is now above it was below the 

 sea. No true marine Miocene beds have been 

 recognized in any part of the Caribbean, An- 

 tillean or Middle American region. Florida 

 alone shows Miocene, not only about the south- 

 ern borders of the group of islets which formed 

 the nucleus of the present peninsula, but also 

 across the neck of the peninsula ; which in Mio- 

 cene times was a wide, shallow strait between 

 the islands and the mainland of Georgia and 

 has been named the Suwanee Strait. 



Secondly, this Oligocene (formerly called 

 Miocene) time was warm, but the true Miocene 

 was a relatively cold period and is marked by a 

 climatic change so sharp that the marine Oligo- 

 cene fauna was almost wholly driven out of the 

 Gulf and Floridian region, which was invaded 

 by a cool-water fauna from the north, corre- 

 sponding to the present fauna of New Jersey. 

 The Arctic and Alaskan leaf beds, called Mio- 

 cene by Heer, are now generally referred to 

 some part of the Eocene column, and in Alaska 

 are overlaid by the cooler marine fauna of the 

 true Miocene. In the Pliocene, on the other 

 hand, at least in Florida and the coast northeast 

 of it as far as Chesapeake Bay and probably to 

 Martha's Vineyard, there was a change to a 

 warmer marine condition, which carried several 

 semi-tropical forms of mollusks as far north as 

 Massachusetts, and was accompanied by a 

 slight subsidence in the Gulf region and on the 

 Central American coast. In Tehuantepec the 

 coastal plain was submerged to a depth of at 

 least 600 feet, though whether the connection 

 between the two oceans was renewed is not yet 

 known. The ice age was, in the Gulf region, 

 ushered in by a slight elevation of the land, and 

 a return to slightly cooler conditions of the sea, 

 but not to as great a degree as during the Mio- 

 cene, the northern current, if any, being prob- 

 ably diverted o£F shore or cut off entirely. 



Lastly, there is no reason, paleontologically 

 speaking, for believing that the Antilles or the 

 Florida peninsula has ever been connected with 

 South America since the Mesozoic, if at all. 

 On the contrary, there are strong reasons for 

 believing that the insular condition has been 

 maintained in nearly all the islands (excluding 

 Trinidad and those adjacent to it) from an early 



period in the Eocene to the present day. It is 

 probable that the distribution of the flora can 

 be fully accounted for without resorting to the 

 hypothesis of an unbroken land connection. 

 Wm. H. Dall. 

 Smithsonian Institution, November 12, 1900. 



PALEONTOLOGICAL NOTES. 

 THESPESIXrS VERSUS CLAOSAUEUS. 

 In 1856 Dr. Leidy described in the Proceed- 

 ings of the Academy of Natural Sciences of 

 Philadelphia two vertebrfe and a proximal pha- 

 lanx, for which he proposed the name of Thes- 

 pesius occidentalis, stating that they probably 

 came from some Dinosaur, although they might 

 prove to be mammalian. Comparison of these 

 bones with the similar parts of Claosaurus an- 

 nectens of Marsh shows them to be identical and 

 that consequently this Dinosaur must be known 

 by Leidy' s name. 



A NEW LOCALITY FOB THESPE9IUB. 



The U. S. National Museum has recently re- 

 ceived from Mr. Harvey C. Medford, of Tupelo, 

 Miss. , the greater portion of the right femur of 

 a large Dinosaur obtained near that place. This 

 femur agrees exactly with the corresponding 

 femur of a large and very complete specimen of 

 Thespesius occidentalis collected by Mr. J. B. 

 Hatcher in Wyoming, and certainly belongs to 

 the same genus if not the identical species. 

 This is the most southern locality for Thespesius, 

 if not the first record of Dinosaur remains in the 

 State of Mississippi. 



THE DERMAL COVERING OF THESPESIUS. 



The impressions of the dermal covering of 

 Tliespesius (Claosaurus), noted by Mr. Hatcher in 

 Science for November 9th, are of great interest, 

 although they are not the first that have been 

 discovered. Some years ago the U. S. National 

 Museum obtained from Mr. Eobert Butler a 

 fine skull of Thespesius, together with other 

 bones, and several pieces of sandstone bearing 

 - the impressions of small horny scutes, similar 

 to those described by Mr. Hatcher. 



THE DENTITION OF BASILOSAURUS CETOIDES. 



In the American Naturalist for August, 1894, 

 attention was drawn to the fact that at least the 

 lower molariform series of Zeuglodon contains 



