EQ0ISETITES. 59 



figures we may consider the French specimens as probably identical 

 with, or at least closely allied to, the British species. 



Heer 1 compares his Siberian species, Phyllotheca sibirica, with 

 Phillips' Equisetum laterale, but recognizes certain small differences 

 which he considers of specific value. There is, however, so close 

 a correspondence between Heer's figures and some examples of 

 the Siberian plant in the British Museum collection and certain 

 of the Yorkshire specimens, that it would seem very probable the 

 two plants are not specifically distinct. 



The specimens figured by Raciborski 2 from the Cracow Jurassic 

 rocks as Equuetites llandus present a close agreement with such 

 examples of E. columnaris as those shown in Figs. 4 and 5, 

 PL XIX., and in Text-fig. 3. 



Although no fertile shoots of E. columnaris have been recognized, 

 it is reasonable to assume that they were of the same type as the 

 strobili of recent Horsetails, with which the cones of some other 

 Mesozoic species of Equisetites closely agree. 



It is practically impossible to discriminate accurately between 

 many of the Mesozoic Equisetaceous stems, or to give definite 

 diagnostic characters, but it is at least probable that Equisetites 

 columnaris is specifically distinct from the more slender Wealden 

 species Equisetites Lyelli, Mant. 3 The latter species never reached 

 the same girth as the older plant, and the more robust habit of the 

 Inferior Oolite and Triassic Horsetails seems to be a well-marked 

 feature of some importance. 



Some of the older species of Equisetites, e.g. E. Muensteri, bear 

 a fairly close resemblance to E. columnaris, and, while probably 

 specifically distinct, the former plant must be considered, as Schenk * 

 suggests, an analogous species. The specimens figured by Andrae 8 

 from Steierdorf and by Tenison- Woods ' from Queensland are too 

 imperfect to admit of satisfactory identification, but the fragments 

 figured by these authors as Equisetum laterals and E. rotiferum 



1 Heer (77), vol. iv. (2), p. 43, pi. iv. fig. 2; vide also Heer (78), vol. v. (2), 

 p. 4, pi. i., and (82), ii. p. 9. 



2 Raciborski (94), pi. xxvii. p. 233, figs. 17-27- 

 Seward (94), pi. i. 



Schenk (67), pi. ii. p. 14. 



5 Andrae (55), pi. vi. figs. 1-5. 



* Tenison-Woods (83), pi. vi. figs. 5 and 6. 



