22 FOSSIL PLANTS. 



BYTHOTREPHIS, Hall, 1847. 

 Palffiontol. New York, vol. i. p. 8. 



Bythotrephis Scotica, Kidston, sp. nov. 



Btithotrephis, sp. 



Kidston, Trans. Eoy. Soc. Edinb. vol. xxx. p. 534, woodcut. 

 Description. Frond frequently dichotomising, filaments contracted at the 



^flemor**? When writing my report on the fossil plants collected by the 

 Geolooical Survey of Scotland in Eskdale and Liddesdale,* the examples of 

 this afga at my disposal were not sufficiently perfect to justify me in applying 

 to them a specific determination. 



From specimens of this plant lately acquired for the Geological Department, 

 I am now enabled to supplement my original description. 



Two of these examples are particularly good. The larger most probably 

 represents a portion of a frond from near the base. All the filaments are 

 broken, and the lower part of the fossil also appears to be incomplete. 

 This specimen, which is fully six inches long, illustrates well the dichotomous 

 division of the frond. The lower part of the fossil is half an inch broad, but 

 about three-quarters of an inch from its base it swells out considerably, and 

 is here 9-10ths of an inch wide, but this width most probably represents the 

 measurement of two contiguous filaments, and though the fossil does not here 

 show any line of division, in all likelihood the separation of the filaments 

 extended further down, but from their close proximity the line of separation 

 has been obliterated through pressure. 



These branchlets again dichotomise, the segments becoming more narrow, 

 till at their upper extremity, where they are broken over, they are only one- 

 fifth of an inch broad. 



In the other example, which is only 2| inches long, the length of the 

 branchlets between the bifurcations is not so great as in the previous 

 example, and it is most likely a portion of the frond nearer the apex. 



Immediately above its base it divides into two branches, each of which 

 again dichotomises. These attain rather more than an inch in length, and 

 give rise to a third set of dichotomous filaments. The branchlets which arise 

 from a dichotomy are slightly contracted at their base, and the summit of the 

 filament from which they spring is also constricted. In no case have I been 

 successful in observing the termination of a filament, but from the manner in 

 which they regularly decrease in width there is probably only a very small 

 portion of the upper part of the smaller specimen wanting. 



As the filaments are frequently bent over each other, the alga has evidently 

 been flaccid. 



The fossils are represented on the matrix by a well-defined carbonaceous 

 stain, and from the quantity of carbonaceous matter adhering to them here 

 and there, the plant must have originally possessed considerable consistency. 



Horizon. Cement-stone Group, Calciferous Sandstone Series. 



Locality. British. Dumfriesshire : Glencartholm, Eskdale. 



EQUISETACE^E. 



CALAMITES, Suckow, 1784. 

 Act. Acad. Theod. Palat. vol. v. p. 359 (fide Unger). 



DiBerent opinions are held by some authors as to the structure of the 

 outer surface of the bark of Calamites, whether it was smooth or furrowed. 

 Almost all Continental Botanists accept the latter view, but some British 



* Trans. Roy. Soc. Edinb. vol. xxx. 



