50 MAECHANTITES. 



shows a distinct and comparatively broad darker median band, with 

 lighter-coloured and thinner margins. 



The specific name erectm proposed by Leckenby in 1864 is 

 adopted in preference to the older term arcuatus, because the 

 specimen to which Lindley & Button applied the latter name 

 was much more imperfect than Leckenby's type, and it is not 

 certain, although highly probable, that the two are specifically 

 identical. Leckenby's type - specimen presents a striking re- 

 semblance to some recent members of the Marchantiese, and, as 



FIG. 2. Marchantites erectus (Leek., ex Bean MS.). Woodwardian Museum, 

 Cambridge (Leek. Coll., No. 1). Nat. size. 



Nathorst also suggested, it would seem to be more fitly referred 

 to the Liverworts than to the Algae. Leckenby, in defining the 

 species, speaks of the occurrence of "fructification in one or more 

 rows of ovate vesicles immersed in the frond," l but an examination 

 of the type -specimen does not reveal any characters suggestive of 

 organs of fructification. The best examples of this plant are those 

 in the Leckenby Collection ; in the York Museum there are a few 

 specimens of M. erectus labelled Sphcerococcites arcuatus. 



The present species of Marchantites bears a close resemblance 

 to M. Zeilleri, Sew., 2 from the Wealden rocks of Sussex; the 

 two may be identical, but the habit of the older form appears 

 to be more spreading and open than in the Wealden species. 

 A small and imperfect fragment has been described by MM. 

 Fliche & Bleicher 3 from the Lower Oolite rocks of Nancy, 

 under the name of Marchantites oolithicus, but the material on 



1 Leckenby (64), p. 81. 



3 Seward (94), p. 18, pi. i. fig. 3. 



3 Fliche & Bleicher (82), p. 67, fig. 1. 





