S8 KOYAL SOCIETY OF CANADA 



T. occidenitale of Newberry. The latter is known by its foliage only, 

 and it therefore otters no satisfactory means of comparison in the pre- 

 sent instance^ although reported by Mr. J. B. Tyrrell as occurring in 

 the Paskapo'O series of the CaJgary region.^ T. distichum miocenum 

 of Heer is also known only tluough its leafy branches, and there is 

 reason for the belief that it is only a form of the species and not a 

 well marked variety. We are therefore throwTi back upon T. dis- 

 tichum as oifering the only satisfactory point of comparison. As pre- 

 viously recorded/ this tree is known through its wood as occurring in 

 the Eocene of the Great Valley and Porcupine Creek, Assiniboia. If 

 we accept the foliage of T. distichum miocenum as representing the 

 species fonn, then the geographical range becomes a very wide one 

 throughout Eocene and Miocene times, and it is necessary to consider 

 if the present specimen falls within this range, or if it extends it in any 

 way. 



A close comparison of the wood of T. laramianuni and T. dis- 

 tichum shows a very close agreement between the two, and in fact the 

 agreement is so close as to establish practical identity, with the excep- 

 tion of one feature, which serves to definitely separate them from one 

 another. In the existing T. distichum, as also in its fossil representa- 

 tive, the bordered pits are in one row, though often paired, and thus 

 becoming imperfectly 2-rowed. In T. laramianum, on the contrary, 

 the pits are definitely croiwded into 2-3 compact rows, a feature which 

 is well defined throughout the spring wood. On the basis which has 

 been adopted for the limitation of species,^ tliis defines a separate 

 species; while yet further, in aocordan'ce with the evidence of reoeoat 

 anatomical studies, w-e must accept such a structural variation as 

 evidence of a m-ore primitive type of development."^ The conclusion 

 to Avhich these facts point is that T. laramianum is somewhat more 

 primitive than T. distichum, of which it may possibly be the ancestral 

 fonn, inasmuch as the latter is at present unknown in any fonnation 

 older than the Eoioene. This hypothesis would be fully sustained 

 on geological grounds were the former kno^m to the Cretaceous; but 

 according to Mr. Tyrrell's report en the geology of the Bow river and 

 its tributaries,^ the formation at Cochrane is of Eocene age as repre- 

 sented by the Paskapoo beds, which include both the Porcupine Hills 

 and the Willow Creek series of Dawson. It is therefore evident that 

 T. laramianum and T. distichum belong to essentially the same horizons 



^ Rept. Geol. Surv., Can., 1886, 136 E. 



= Trajis. R.S.C., IX., iv., 36. 



' Amer. Nat.. XXXVIII., 1904, p. 255 et seq. 



* Amer. Nat.. XXXVIII., 1904. p. 267. 



= Rept. Geol. Surv.. Can.. 1886, 56 E. and 136 E. 



