12 Later Extinct Floras of North Ameri* 



given, the affinity si 1 must be lered to some extent 



conjectural. 



Formation and Locality. Red ferruginous sandstone of 

 Lower On is formation, Blackbird Hill, Nebraska. (Dr. 



i [ay den. * 



Pyrus cretacea. (n. sp.) 



Leavt - petioled, small, roundish-oval or elliptical, often Blightly 

 emarginate, entire or finely serrate; medial aerve strong below, 

 rapidly diminishing toward tjie summil : lateral nerves lour or five 

 pahs w itli intermediate smaller ones, diverging from the midrib at 

 unequal angles, curved toward the summits, where they anastomose 

 in a series of arches parallel with the margin ; tertiary nerves 

 forming a network of which the areola- are somewhat elongated. 



There are a number of leaves in the collection, of which the 

 characters, as far as they arc; discernible, agree more closely 

 with those of the species of Pyrus than with any other with 

 which I have compared them. All the traces of their origi- 

 nal structure which remain, however, are quite insufficient to 

 permit their generic limitation to l" 1 determined with any de- 

 gree of certainty. The leaves of many of the allied genera of 

 the Rosacea have so much in common, that even with the 

 Leaves of the living plants it would be difficult, if not impossi- 

 ble, to -emirate them. The fossils before us are, however, very 

 characteristic of the formation which contains them, and for 

 that reason require notice, and a- far as practicable description. 



There are several other leaves in the collection which seem 

 to me io have belonged to Rosaceous tree-, and there is per- 

 haps no apriori improbability that Pyrus began its existence 

 on this continent with its and companions in our 



forests of the present daj . 



Formation <n<<l Locality. Lower Cretaceous Bandstone, 

 Smoky I lill, Kansas. 1 1 >r. 1 [ayden. » 



liirioili'iiilron priiiiu'vimi. (n. pi 



I.' ree-lobed, upper lobe emarginate, all the lobes round- 



nervation delicate, principal nerve straight or slightly curved, 



