58 STUDIES IN GEOLOGY, No. 4 



Zigno long ago (1885) figured an Italian Jurassic Otoza- 

 mites in close association with a Williamsonia fructification 

 and Wieland has brought to light many similar associations 

 so that one is perhaps justified in referring the genus to the 

 order Williamsoniales. The structure of the epidermis was 

 partially described by Schenk 13 and more fully by Thomas 

 and Bancroft. 14 The epidermal cells have sinuous walls and 

 the stomata, which appear to be confined to the lower sur- 

 face of the pinnae, have guard cells with hemispherical or 

 fusiform thickened patches like those of some Zamites pin- 

 nae. In Otozamites Feistmanteli Zigno, Thomas and Ban- 

 croft found about 100 stomata per square millimeter which 

 formed almost continuous rows between the veins. 



In describing material it is important to discriminate be- 

 tween the upper and under surface of the frond which may 

 show considerable differences due to the size of the midrib 

 and the position of the pinnae, and the latter also show con 

 siderable variation in form and orientation according as they 

 represent basal, medial or apical portions of the frond. 



Many species have been referred to Otozamites and this 

 type is very abundant from the late Triassic through the 

 Jurassic and sparingly in the early Lower Cretaceous. 



Otozamites is very poorly represented in North America 

 and chiefly in rocks of older Mesozoic age. Thus four 

 species have been recorded from the Triassic, two from the 

 Lower, one from the Middle and one from the Upper Jur- 

 assic. None are known from the Lower Cretaceous of North 

 America even from beds such as the Knoxville and the Mor- 

 rison which at times have been considered Jurassic. The 

 genus is not represented in the older Potomac formations of 

 the East Coast in the assemblage which contains very many 

 Wealden and Neocomian ferns, cycads and conifers. Sim- 



13 Schenk, A., Wiirzb. Naturwiss. Zeits. Bd. 6, p. 10, pi. 34, fig. 

 7, 1867. 



"Thomas, H..H., and Bancroft, N., Trans. Linn. Soc., vol. 8, pt 

 5, p. 186, pi. 19, figs. 3, 4, 1913. 



