32 PRIMOIIDIAL PERIOD. 



CHAPTER III, 



LOWER SILURIAN AGE. 

 PPJMORDIAL PERIOD. 



PLANTS. 



CRYPTOGAMIA. 

 Class THALLOGENES. 



Genus CRUZIANA D'Orbigny, 1842. 



Cruziana Linnarssoni White. 



Plate I, fig. 2 a, 6, and c. 



Cruziana Linnarssoni White, 1874, Geog. & Geol. Exp. & Surv. west 100th Meritl., 

 Prelim. Rep. luvert. Foss., 5. 



Body not mncli flattened, oblong or subelliptical in outline, but nar- 

 rowed and more or less pointed at the ends, one of wbicb is a little more 

 acutely pointed than the other ; median fuiTow traversing the whole length 

 of the body, the greater part of it being deep and distinct, but a part of it 

 is usually more shallow. 



Smface marked by few or no transverse rugae, but upon the more 

 pointed end of some of the specimens thei'e is a secondary ftuTOw upon 

 each side of the median fuiTow ; these converge to the point where they 

 join the median furrow, but they disappear in the opposite dnection before 

 reaching the middle of the body. Upon others, an incipient fiuTow is some- 

 times seen at each side of the half of the body that is more acutely pointed 

 These are near to, and their dhection is parallel with, the sides of the body. 

 This character is shown in figure 2 a and h, Plate I. Stipe rather small, 

 attached about midlength of the body in the bottom of the median furrow, 

 but it is, however, rarely preserved. 



