8 



Having brouglit our investigations of the cycadean 

 family to tiiis point, I now beg to direct your attention 

 to the examination of two fossils, which I am enabled 

 to bring to your notice through the courteous kindness 

 of Mr. Clifton, Governor of Her Majesty's Convict 

 Prison at Portland. 



MANTELLIA. Brongniart. 

 Cycadeoidea, Buckland, Proc. Geol. Soc. Vol. i., p. 80. 

 Cycadites, BuckL, Geol. and Min., p. 496. 

 Echinostipes Porrie. 



Trunk cylindrical, covered with the long permanent 

 bases of the petioles, medulla entirely cellular, with 

 numerous gum canals. Wood consisting of a cylinder 

 of striated tissue every where penetrated with 

 medullary rays. Fruit borne on secondary axes 

 generally protruding beyond the bases of the petioles. 



Mr. Carruthers retains Brongniart's name in prefer- 

 ence to that of Cycadeoidea given provisionally by 

 Buckland, but afterwards withdrawn by him in favour 

 of Cycadites under the erroneous idea that MantelUa 

 was doing service for a genus of sponges. Mr. 

 Carruthers says on this subject : — " Were Buckland's 

 name unobjectionable it ought to be retained because 

 of its priority by a month or two, but as it originated 

 in an error, was withdrawn by its author, and is in 

 itself, as Brongniart and others have said, obj ectionable, 

 it seems necessary to reject it in favour of MantelUa." 



The trunks of this genus are usually silicious, the 

 beds surrounding them being much impregnated with 

 silex ; their growth must have been very slow, as may 



