240 THE FLORA OF THE DAKOTA GKOLTP. 



etc. No species, liowever, of piuuiitely lobed leaves of Fieus is represented 

 iu more recent stages of the Tertiary of Nortli America, wliere the fi'enus 

 seems to gradually disappear. In the iiora of tlie auriferous gravel 

 dejjosits of California, numerous leaves of F. filfefolki have l)een found with 

 some others described as new species, but with characters so closely allied 

 to those of the normal form that they may represent mere varieties of it. 

 In the Pliocene, as in the present tlora, the More;r, forced southward by a 

 gradual lowering of the temiierature, have left the continental part of North 

 America, remaining still present represented by three species of Ficus, 

 wliich inhabit the southern end of the })eninsula of Florida, while two 

 sptM'ies of Morns, recently introduced from Japan or derived from F. lil'ue- 

 fofid, remain as beautiful trees of our forests. 



Tlie faiiiilv Laurinefe is distinctly represented and easily recognized iu 

 the Hora of tlu^ Dakota Group, not only by the peculiar characters, form, 

 and nervation of the leaves, but still more by the presence of some well 

 preserved fniits, jjositlvely i-eferable to Laurus or another genus of Laurinefe. 

 There have been described up to the present time, from vegetable remains 

 I'ouiidintho Dakota Group, eleven species referred to Laurus, four to Persea, 

 fi\-e to (Jinnamomum, one to Oreodaphne, two to Lindera, eleven to Sassa- 

 fras, or twenty-six species omitting those of Sassafras (Araliopsis), eight 

 species which, as far as known now, have an equal degree of affinity with 

 Sassafras and Aralia. From the schists of Atane, Iltser has described four 

 species of Laurus, one of vSassafras, and one of Cinnamonuim. Of Laurus, 

 two species are identified at Atane and in the Dakota Grouj), and one Cin- 

 nainomum (C. se^annn/se), is recognized not only in the Cenomanian of 

 Greenland and of Kansas, but also in the Senonian of Patoot and in the 

 Eocene of Sezanne. The dif<tribution of that species, or its presence at 

 Patoot, is the more remarkaljle since the Laurinea;, as yet, are compara- 

 tively rare in the xVmerican Senonian, where three species only are recorded 

 from Patoot, and one from the Princeton collection made in Wyoming. In 

 the Laramie Group the Laurineaj are represented by eleven species, six of 

 them descnbed by Prof. Ward; a single one, a Cinnamomum, has been 

 found in the Green River Gi'oup. From the Miocene, especially of Cali- 

 fornia and ( )regon, five species of Laurinefe are recorded. 



Tlie leaves of Laurus, though variable in their form and in some details 

 of their nervation, the characters, especially considered for the determina- 

 tion of tlie s])ecies, are mostly of the type of Laurus pi hiiuioiht, and repi'e- 

 sented iu the Dakota Group in the leaves of L. priinhfeiua var cretacm. The 



