Cope.] 1*^° [.Jnlj-1!5, 



internal snrface are easily distinguished, and the distinct natures of the 

 lamellar and prismatic layers have been evidently well understood by the 

 artificer, who has ground away the latter in order to put a sharp edge on 

 the former at one end. This edge is sharp, and mainly well preserved. 

 The implement has a greater median width, and smoothly ground thick 

 margin ; the end of the plate is obtuse and with thick edge, almost en- 

 tirely composed of the prismatic layer. It has evidently been held in the 

 hand, and been used after the manner of the stone chisels of the North 

 American Indians. 



The cotemporaneity of man with postpliocene Mammalia in Europe 

 and North America may be considered as established. It is, however, an 

 important question to decide whether man occupied successively regions 

 more and more remote from a supposed place of origin by migration, or 

 whether a cotemporary postpliocene existence can be traced over the 

 whole earth. His remains were not fovmd by Lund after remarkable and 

 extensive investigations into the postpliocene cave fauna of Brazil, 

 though human remains from caves not far from Rio Janeiro, are in the 

 Academy's Museum. What the precise age of these is, cannot now per- 

 haps be stated. On the Peninsula of Florida Prof. Wyraan has found 

 remains of Man, but not associated so far as I can ascertain with any ex- 

 tinct species of Mammalia. 



The present shell-chisel was found by Rijgersma under circumstances 

 precisely similar to those attending the discovery of the gigantic rodents. 

 Some portions of each of the species described were embedded in the 

 breccia, and others occurred loose in a red earth in cavities of the breccia. 

 The chisel has the color and constitution of the latter teeth and bones, 

 and was found with them in this earth. Some of the teeth are even 

 more fresh looking and less stained than the chisel. Though the evidence 

 is not quite conclusive, yet the inference is very strong that the Amblyr- 

 hiza and Loxomylus had human cotemporaries. 



If now these large herbivorous animals lived before the submergence 

 of the mountains, whose peaks the present Virgin and other West Indian 

 Islands are, we are enabled, with due regard to the slenderness of the 

 evidence, to suggest human co-existence with that great geological event. 

 A probability is thus added in favor of the lateness of the period of sub- 

 mer<>-ence of a former Caribbean continent, as already suggested by 

 Pomel. 



in. On two extinct Marine Mammalia from the United States. 

 AxoPLONAssA, Cope. 



This genus is represented by a considerable portion of the mandible. 

 No other fragment has as yet come under my observation. The portion 

 does not extend posterior to the symphysis, but the latter is very long, 

 and the rami slender, indicating a form of muzzle quite like that of a 

 gavial or a Squalodon. It is strikingly different from the latter genus in 

 beino- for the most part edentulous. The foramina of the dental arteries 

 issue numerously along the outer jnu'gin of the superior face of the 

 ramus, and are more or less cannectecl by a longitudinal groove. Shallow 



