294 



Guological Society. 



Fructifications. 

 Benneitites spp. 

 Williamsonia gigas. 



WilUaynsonia spectabilis. 

 Williamsonia ivhitbietisis. 

 Wielandiella angnstifolia, 



Williamsoniella coronata. 



The followinsj table gives the proved, or probable, associated 

 jvirts of some members of the group : — 



Foliage. Trunk. 



Zamites spp. BennettHes spp. 



Zamitea gigas. Attached, no separate 



name. 



Otozamites sp. 



Ptilophyllum pectinoiden. 



Anomo zamites minor, (Only slender branches 



knowTi, no name.) 

 r«n iopteris vitta ta. 



Dr. Stopes exhibited slides of microphotographs of the stem 

 and It'af-hase anatomy of the group, including some unpublished de- 

 tails of Benneitites maximns. The roots of the group have hitherto 

 been entirely unknown, and a slide was exhibited for the finst time 

 showing rootlets penetrating the leaf-bases of a petrilied specimen 

 (represented by a section in the Geological Department of the 

 British Museum — Natur.il History). These roots probably belong 

 to JB. saxhyamts : they are covered with wonderfully petrified 

 root-hairs, running uncoUapscd through the silica matrix. They 

 raise intei'esting questions concerning the possible chemical con- 

 ditions of the infiltration of the silica. Illustrations were also 

 exhibited of the famous complex ' flower ' and cone-structures, and 

 of Wieland's brilliant restorations of the same. Microphotographic 

 slides were exhibited of the seed-cone of an interesting unpublished 

 new species from the British Gault. This is beautifully petrified, 

 and adds to our knowledge of the finer anatomy of the seeds and 

 associated structures. It is also the largest cone of the Bennettitales 

 yet known, though it occurs in the Gault, by which time the group 

 appears to have begun rajiidly to die out. 



The following table indicates the distribution of a few of 

 the most interesting representatives of the Bennetti- 

 tales ( including the cohorts Bennettitea? and William- 

 soneae) : — 



Upper Cretaceous. 



Very fragmentary iand uncertain recorda ; apparently 

 the group is nearly or quite extinct. 



Middle Cretaceous ; The new large-sized seed-cone. 



Gault. B. morierei $ (P described originally from the Jurassic). 



Lower Cretaceous ; Well-petrified trunks with fructifications. 



Lower Greensand. B. gibsonianus (type-species of the Bennettitese). 



Potton Sands. 

 Wealden. 



Jurassic; Purbeck. 



B. maximus, 



Tjunks, e.g. Colymbetes edwardsi. 



Trunks (casts and petrifactions), 



foliage. 

 B. saxbyamis. 



Trunks (casts and semi-petrifac- 

 tions), i. 



Buckland's original Cycadeoidea 

 spp. 



('. gigantea. 



Throughout 

 these periods 

 in America, 

 trunk-remains 

 very abun- 

 dant, often 

 petrified and 

 with fructifica- 

 tions, parti- 

 cularly from the 



Black Hills, 

 South Dakota, 



