138 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



boidal areas placed in spiral series, and in the elevated cushion 

 on which is situated the scar of the organ it has borne. It is 

 true that in Stigmaria there is a slight circular cushion which 

 bears an inner circular ring containing the central single vascular 

 cicatricule, but the raised cushion in Omphalophloios is much 

 more pronounced, and the oval scar of the fallen organ, with its 

 transversely elongated vascular cicatricule is placed above the 

 centre of the cushion on which it sits. In the older condition of 

 Omphalophloios, as that shown at fig. 26, f and G, these 

 characters are in part effaced with age, but it is to the more 

 active growing parts that we must look for the true structure of 

 the cushion and scar. 



It also differs from Stigmaria in the presence of the small 

 cicatricule on the lower margin of the raised central cushion. 

 This structure is seen both in the young and old conditions of 

 the fossil (Fig, 26, b d, g d), though it is not always discernible, 

 possibly through imperfect preservation. In position it agrees 

 with a similar structure seen on the cushions of some species of 

 Lepidophloios, and which from its position can scarcely be com- 

 pared with the so-called ligule scar of Lepidodendron and 

 Sigillaria. 



I believe Omphalophloios is a rhizome whose general structure 

 approaches closely to that of Stigmaria, but the differences, to 

 which reference has already been made, are such as to demand 

 its removal from Stigmaria, in which genus I have always felt it 

 did not find a suitable place. 



It should be mentioned, however, that in some forms of 

 Stigmaria the scar is surrounded by a more or less distinctly- 

 defined rhomboidal area, as in Stigmaria areolata, Dawson, 1 of 

 which I have a similar form from the Lower Carboniferous of 

 Northumberland (No. 2558), but in these cases the rootlet scar 

 is of the normal Stigmaria type, and such specimens are 

 probably from that portion of the stem of Lepidodendron when 

 the transition between stem and rhizome takes place. 



If my views on the identity of the English and American 

 plants are correct, then the genus is restricted to a single species. 



1 Foss. Plants, Devon, and Upper. Silur. Form, p. 23, t*l. III., fig. 33. 

 1871. 



