Genus Pothocites, Paterson. 313 



In the course of development, we have every reason to be- 

 lieve that during the maturation of the spike the internodes 

 would become elongated ; so probably this difference in general 

 outline is only indicative of a different state of development. 

 It agrees with Pothocites Grantonii in all other respects. 



The absence of nodes on the stem of P. Grantonii seems to 

 be entirely due to changes it has undergone during minerali- 

 zation. The specimen from Barnton Pavement-stone Quarry 

 has also no indication of nodes on the stem ; but, from the 

 evidence afforded by the other specimens, there can remain 

 little doubt as to both it and P. Grantonii having originally 

 possessed stems similar in this respect to the other examples. 



In regard to Pothocites Patersoni, Eth. ? the chief characters 

 on which this species was founded consisted in the absence of 

 the stellate sporangia and the presence of the " transverse 

 bars." I have already mentioned that there are distinct indi- 

 cations of the stellate-like sporangia, and that the degree of 

 prominence of the transverse bars depends greatly on the 

 physical conditions under which mineralization has taken 

 place. 



In the plant I provisionally named Pothocites calamitoides 

 the transverse bars are very distinctly seen, and associated 

 with them we have the stellate sporangia placed upon their 

 little knob-like extremities. 



For these reasons, as well as the evidence afforded by the 

 detailed descriptions of the various specimens, I believe that 

 all these fossils are to be referred to Pothocites Grantonii y 

 Paterson, and, further, that this plant is not a distinct and 

 separate species, but the fructification of a species of Bornia ^ 

 Horn., probably of Bornia radiata, Brongn. sp. 



EXPLANATION OF THE PLATES. 



Plate IX. 



Fig. 1. Fruit of Bornia radiata, Brongn. (Pothocites Grantonii, Paterson). 



The fruit shows two perfect segments and a portion of a third. 

 Each segment has several longitudinal ridges bearing sporangia 

 which have opened. (Nat. size.) From the Calciferous Sand- 

 stone series, shore, at Granton. 



Fig. 2. Portion of the uppermost segment of the same specimen, showing 



the arrangement of the sporangia. (Magnified.) 



Fig, 3. An open sporangium composed of five rays, from the same speci- 

 men. (Magnified.) 



Fig. 4. Another sporangium, with four rays. (Magnified.) 



Fig. 5. Diagrammatic section (at right angles to the surface) of one of the 



rays on Pothocites Grantonii y Pat., showing that the apparent 

 " border n to the rays is caused by an upward turning of their 



margins. 



Ann. & Mao. N. Hist. Ser. 5. Vol. xi. 22 





