PRESIDENT'S ADDRESS. Ixi. 



GEOLOGY. 

 A FOSSIL CYCAD. 



Mr. A. M. Wallis, one of our honorary members, called my 

 attention last year to a cycad he had recently found in the Lower 

 Purbeck beds of Portland considerably higher up than the Dirt 

 beds. I saw that it differed from the forms usually found 

 in the island, and retained the character of the family 

 Cycoidea in its net-work of persistent petiole bases, but instead 

 of being dwarfed, like C. megalopliylla and G. microphylla, it 

 was more than three feet high, measuring three feet seven 

 inches in the girth. A striking feature of this cycad is the 

 conical bud enclosed by tapered bud-scales. The surface of the 

 stem presents the appearance of a prominent reticulum of pro- 

 jecting ridges, of which the meshes were originally occupied by 

 the persistent bases. The substance of the leaf-stalks has for the 

 most part disappeared, and there is no trace of any inflorescence. 

 Though there is no instance of the occurrence of Cycaclete in the 

 Paleozoic beds they are abundant in the secondary, and so well 

 preserved are they that they can be determined without any 

 difficulty. Although they have not yet been found in the beds of 

 the Tertiary age there is no doubt that they are not absent, as 

 cycads are now living in the tropics. In 1828 Brongniart 

 established a genus of fossil cycads, to which he gave the name of 

 Mantellia, and in the same year Dr. Mantell described two species 

 from the Isle of Portland, one of them being the same as the English 

 species of Brongniart. The trunk of the cycad has no true bark. 

 Its outer covering is composed of persistent scales, which formed the 

 bases of the fallen leaves, making a compact envelope, supplying 

 the place of bark. No leaves are found in connection with the tree. 

 This may be owing to the forest having been gradually submerged, 

 and as the leaves decayed they were swept away by the tides, 



ICHTHYOSAURUS AND PLESIOSAURUS. 



It is not a long time since the skeleton of an Ichthyosaurus 

 was found in the Lias of Wurtemberg with the outline of the 



