SIGILLARIA 213 



types of more or less decorticated surface noticed under 

 Lepidodendron recur here. One very characteristic form 

 may be noticed, to which the name Syringodendron has 

 been given. In this, the epidermis and the leaf-scars 

 have perished ; the ribs — if the specimen belonged to 

 the Eu-Sigillariae — remain, and are marked by the same 

 prints which occur in the typical leaf-scars. In these 

 cases, the middle print — that marking the leaf-trace 

 bundle — is usually inconspicuous, while the two lateral 

 lines of the parichnos are extremely marked. Cor- 

 responding forms of preservation, without the ribbing, 

 occur in the Sub-Sigillariae. The Syringodendron char- 

 acter may also be found, even on the epidermal surface, 

 at the base of the old stems, where excessive growth in 

 thickness has obliterated the leaf-scars. Fig. 86, from 

 Sigillaria tessellata, one of the Favularian forms, shows 

 the surface exposed at three different levels. At ep 

 the natural epidermal surface is shown, with the char- 

 acteristic hexagonal leaf-scars, each of which shows the 

 three prints (representing the vascular bundle and the 

 double parichnos) as described above. On the part 

 marked c l , the superficial layers, with the leaf-scars, have 

 peeled off, exposing the outer cortex, on which the longi- 

 tudinal ribs come out more clearly than before. The 

 leaf-trace bundles are still evident ; the two parichnos- 

 scars have united below each vascular bundle, forming 

 a crescent. At <? the process of destruction has gone 

 deeper ; a considerable thickness of cortex has broken 

 away, and a deeper layer is laid bare. The ribs are 

 still evident ; the fused parichnos-scars show conspicu- 

 ously as lenticular outlines, but the vascular bundle 

 within each loop is not visible. This lowest level may 



