[MATTiiKwJ A REVIEW OF THE LITTLE RIVER GROUP 



113 



finely striated, branches not numerous ; leaves long, several times bifur- 

 cated, with slender segments, almost filiform, arched; fructification in 

 spikes, groups ( ?) of fertile verticiles alternating with foliar verticiles; 

 sporangipliores enlarged to a shield C^) on which are inserted 4 ('P) 

 sporanges; structure of the stem unknown." 



" THiat is known of Arcliœocalamites does not enable iis to fix its 

 systematic position. So far there is only one species of the genus." 



Stem. — There is nothing in Lesqnereux's diagnosis (of Bomia 

 radiata) tha.t will separate the Canadian forms from his species, but 

 we find no such variability in the width of the ribs as he described; 

 this will appear from the following table showing the dimensions of 

 stems collected from the Little River terrane: — 



Horizon and 

 Locality 



Fern Ledpces. 



Figured by Dawson ~| 

 Fossil Plant Dev. & \ 

 U. Sil J 



Fern Ledges Nat. His. Society CoU'n . 



Bed 2 Author's cabinet, PI. 1,1 

 I fi^.l / 



Bed 7? 



Author's cabinet. 



" Author's cabinet, perhaps 

 C. Cistii 



Bed 2!Author'scabinet,perhap8l 

 C. Cistii, alternate ribs. J 



Length 

 in mm. 



150 



130 



190 



110 

 180 



110 



80 



Width 

 in mm. 



65 



25 

 35 



37 



41 



34 



30 + 



Inter- 

 nodes 

 in mm. 



105 I 



100 



85 



60 



70 



Number 

 of ribs in 

 1 centim. 



6i 

 6 



6-7 



There is here very little variation in the width of the ribs in the 

 first five examples though the width of the stem and the length of the 

 intemodes vary considerably. But none of these show the base of the 

 ptem, where, perhaps, the ribs were wider, nor the ultimate shoots where 

 the ribs may have been narrower. 



As will be seen the internodes in this species were long, varying 

 from a half longer to four times longer than the width of the stem, 



