FOSSIL FLORA. 717 



central or terminal lobe, all separated by broad, rounded sinuses; midrib 

 very thick below and to the middle of the leaf, from which point it rapidly 

 diminishes to the apex; secondaries numerous, alternate, at angle of 30° 

 to 45°, about 4 in each lobe, except the small central lobe, the upper 

 ones passing to the apex of the lobe, the other curving near the margin 

 below it; short secondaries pass up to and arch along above the sinuses, 

 occasionally in the upper part forking and passing on both sides; nervilles 

 strong, percurrent, nearly at right angles to the secondaries; finer nervation 

 not preserved. 



The specimen figured is the only one obtained of this remarkable and 

 highly characteristic leaf. It is not perfect, yet it appears to represent 

 practically all of the leaf. The part preserved is 14 cm. long and 9,5 cm. 

 broad between the upper lobes. It was probably at least 17 cm. in length, 

 and if there were 7 lobes it was of course much larger. It was probably 

 12 to 14 cm. broad between the lower lobes. The width at the middle 

 sinus is a little less than 3 cm. It is strongly 54obed, and, following the 

 analogy of Artocarpus lessigiana (Lx.) Kn., may have been 7dobed. 

 There is, however, no evidence that it had more than 5 lobes. The 

 lower lobe is 5.5 cm. wide at a distance of 1.5 cm. from the midrib, 

 while the upper lateral lobe is fully 6 cm. wide at the same distance from 

 the midrib. The extreme length of the upper lobe is less than 5 cm., the 

 apex being curved around and up. The secondaries, as pointed out in the 

 diagnosis, are about 4 in number in each lobe. They are about 1 cm. 

 apart, the upper one only entering the apex of the lobe. The only trace of 

 the finer nervation consists of a few strictly percurrent nervilles. 



I am in doubt as to the proper generic reference of this leaf. When it 

 was collected in the field, the conclusion was hastily formed that it was an 

 oak, but the nervation is not at all that of this genus. It seems to have rather 

 a moraceous character, but I have not been entirely successful in finding 

 affinities. It has some resemblance to species of Ficus, but on the whole 

 approaches closest to Artocarpus. Compared with living species it is of 

 the A. incisa type, yet of course differs in marked peculiarities, having, for 

 example, only five instead of many lobes. Among fossil species this undoubt- 

 edly approaches A. lessigiana (Lx.) Kn., 1 found in the Laramie and Denver 

 formations of Colorado, Wyoming, etc. The Yellowstone leaf has much the 



1 Science, Vol. XXI, p. 24. 



