314 



THE GENUS OLDHAMIA IN AMERICA— WALCOTT. 



No other fossils were identified; and the determination of the geologic 

 horizon is somewhat uncertain. 



Genus Oldham ia, Forbes.* 



The best illustrations of Oldhamia are given by Dr. J, R. Kinnahant 

 and Mr. J. W. Salter.| Prof. Brady § discussed the genus and its rela- 

 tions to living forms, in 1865. He proposed to limit the genus to the 

 0. radiataj and to refer the 0. mitiqua to a new genus — Murchisonites. 



OLDHAMIA (MUECHISONITES) OCCIDENS, new species. 



Frond with a jointed, slightly flexuous stem; fan-shaped fronds, 

 formed of numerous simple filaments or attached to the upper end of 

 each joint; the filaments being somewhat longer than the joints and 

 giving the entire frond the appearance of a succession of tufts of fila- 

 ments, each springing from the summit of the tuft below. 



The specimens are preserved as casts on the surface of a smooth sili- 

 ceous slate. No trace of cells or vesicles appear; and the position of 

 Oldhamia in the classification of organic forms is not advanced. The 



FiG.l. Oldhamia (M.) occidens. View of a single frond from the gorpe of the Poestenkill. Natural size. 



suggestion that it is a calcareous alga appears to be as satisfactory as 

 any. This species differs from Oldhamia (M.) antiqua Forbes |1 in the 

 form of growth and arrangement of the tufts of filaments. 



The specimens are from the Cambrian (?) slates. 



The Oldhamia was first found in reddish shales associated with green- 

 ish shales and beds of quartzite, ranging from one to nearly twenty-two 

 inches in thickness, at a saw-mill dam midway between Burden Lake 

 and Nassau Pond in the township of Nassau; again in similar rocks 

 about 2 miles farther up the same stream and IJ miles SSE. from the 

 south end of Burden Lake. It occurs also on the Moordener Kill, 



*Journ. Geol. Soc. Dublin, 1848, vii, p. 184. 

 t Trans. Royal Irish Acad., xxiii, 1859, pp. 547-561. 



tMem. Geol. Soc. Great Britain; Geology of North Wales, 2d ed., 1881, pp. 471, 

 472, pi. 26. 



^ Geol. Mag., ii, 1865, p. 6. 



II Trans. Geol. Soc. Dublin, 1848. 



