186 MR. H. HAMSHAW THOMAS AND MISS N. BANCEOFT ON 



Otozamites geaphicus (Leckenby, ex Bean MS.) n. comb. 



' m 



Fronds of this form, from Marske yield good preparations, but the cuticles are very 



thin and fragile, and hence only small pieces are obtainable*. The similarity of its 



cuticular structure to that of the foregoing types is very noticeable. The upper epidermis 



has small squarish cells with rather thick vralls showing closely approximated folds. 



The loAver cuticle is very thin, with the usual type of cells ; the stomata are rather 



sparsely scattered, only 40-50 per sq. mm. occurring in the specimens examined. In 



this they contrast with Otozamites Feistmcmteli from the same bed, in which the stomata 



are twice as numerous. The stomata are arraniired more or less in lines between the 



veins which are marked by the greater elongation of the epidermal cells ; they have 



a fairly regular orientation, the pore being at right angles to the veins. They are not 

 deeply sunken. 



The stomatal structure (see PL 19. fig. 4) is like that of Zamites. The thickening 

 patches are hemispherical to spindle-shaped, and the central area is thin. The sides 

 of the pore seem to be slightly thickened, and the two lateral subsidiary cells are also 

 somewhat thicker than the other epidermal cells. 



Otozamites Peistmanteli, Zigno. 



The dark shale bed at Marske has yielded good specimens of the smaller Otozamites, 

 which gives good cuticular preparations. These show some interesting points ^ the 

 stomata are clearly seen and are very numerous, being almost contiguous in lines 

 between the nerves. About 100 occur in each square millimetre. In structure and 

 form they are similar to the stomata of the larger species, but the lateral thickening 

 patches thin oTit gradually towards the slit, showing no sharp margin, but more or 

 less merging in towards the central area. The latter is very slightly cuticularised 

 except at the edges of the pore, which stands out clearly as a dark central line {cf. PL 19. 

 fig. 3). The subsidiary cells are again slightly thickened, and their relations to the 

 other epidermal cells are often well seen. 



DiCTYozAMiTES Hawelli, Scward. 



The cuticular structure of Dictyozamites JoJmstrupi, ISiath. has already been described 

 in some detail by Prof. Nathorst (1907, p. 12, Taf. 3. figs. 2-8). The structure o£ the 

 present examples from Marske does not differ materially from that of the Bornholm 

 examples, but the structure of the stomata can now be further elucidated. As in the 

 former cases, the upper epidermis is devoid of stomata, and is composed of cells with 

 very sinuous walls, the reticular course of the veins being marked by the elongation, 

 narrowing, and thickening of the cells above them. The folds in the cell-walls of this 

 species are not so deep as those previously described. The lower epidermis is less 

 strongly cuticularised than the upper ; the course of the veins is again marked by elon- 

 gated cells with less folded ualls. The stomata occur only between the \ eins ; they are 

 more or less irregularly scattered, but still show a distinct tendency to have the pore 



