700 MR. W. CARRUTIIERS ON FOSSIL CYCADEAN STEMS 



B. (jIibsom . is, sj). nov. (Tab. LYIII.-LX.) 



Trunk compressed elliptical, with small medulla, and a thick subcontinuous woody cy- 

 linder; vascular bundles passing almost directly outwards and breaking up into a 

 double series of small bundles, which are parallel to the superior and inferior sur- 

 faces of the petiole, except that a loop is sent down from the upper series into the 

 centre of the petiole. The section of the petiole is subquadrangular. 



W.it r-worn fragments of this species and of B. Saxbyanus have been mistaken for 

 portions of Backlandia anomala. Mantell, in his 'Medals of Creation,' vol. i. p. 163, 

 fig. 57, gives a very good woodcut of one of these fragments, which he has reproduced in 



several of his publications. 



The trunk in the most complete specimen which I have seen is 8 inches long, but it is 

 imperfect at both ends. Mr. Gibson informs me that it was a third longer when he found 

 it. The long diameter is 11 inches, and the short 6^ inches; of this the medulla forms 

 1 inch, the wood \\ inch, and the bases of the petioles 4 inches — the outer, cortical layer 

 being very thin. 



The specimen is beautifully preserved. Prom it I have determined the structure of the 

 genua and the nature of t he • reproductive organs, as explained under the genus. 



The secondary axes have from thirty to forty thick linear leaves arranged in several 

 whorls. In form these leaves agree with those subtending the carpophylls in Cycas 

 ciri'malis ; and their functions were the same : they protected the organs of reproduction. 



They are closely applied to the fleshy receptacle, and are bent over and imbricated on the 

 Qppoi surface. The pollen may have obtained access to the ovules in the same way as 

 Mr. Yato has noticed it is admitted to the ovules of the living species named. He has 

 - tw.1 the compact bud, consisting of the carpophylls surrounded and closely protected 

 the scales, open up and remain spread out for some time—about three days— then 

 firmly close, and remain so until the seeds had considerably advanced. 



From the Lower Greensand at Luccomh Chine, Isle of Wight, Thomas F. Gibson, Esq. [British 



Museum.] 



P>. roniLANDicus, sp. nov. (Tab. LXI.) 



Trunk elliptical, with small medulla, a thin interrupted woody cylinder, and large cortical 



Uular la er, through which the vascular bundles pass out in a slightly ascending 



to the bases of the petioles; the section of the petiole subrhomboidal 



ectlOll 



triangular, with the lower angle very obtuse, the lateral angles acute and produced 



ami the superior base-line of the triangle slightly bent outwards. 



the 



the Geological Society.] 



«. I'lAcni.vM s, sp. nov. (Tab. LXII.) 



Trunk elliptical, very compressed, with a large elliptical medulla, having the narrow ends 



snmewhat produced ; woody cylinder subcontinuous, slightly interrupted at intervals 



du.ctly outwards; petioles m section compressed quadrangular. 



