BY R. M. JOHNSTON, F.S.S. 15 



the Pachydomi of this zone, with their more common 

 associates : — 



Pachydomus globosus J. de Sow. 



„ de Konincki R. M. Johnston. 



„ Hobartensis „ 



„ gigas M'Coy. 



„ carinatus Morris. 



Eurydesma cordata „ 



Notoinya Gouldii R M. Johnston. 



,, trigonalis „ 



„ Bf^ddomeii „ 



A vicuJopecten limae formis Morris. 



„ lUawarensis „ 



„ squamuliferus ,, 



,, Fittoni „ 



Platyschisma ocula J. de Sow. 



Connularia Tasmanica R.M.Johnston. 



Stenopora Tasraaniensis Lons. 



„ informis „ 



Favosites ovata „ 



„ sp. indel. forming broad flat jDatches over a foot 

 in supei'ficial extent. 



(3.) FenesteUa Zone. — Succeeding the Pachydomus 

 beds there occurs a series of thin, friable, shaly, rusty 

 mudstones, more or less decomposed towards the upper 

 surface, and almost wholly composed of the crushed, 

 laminated frond-like layers of the common species of 

 FenesteUa. These beds are now estimated to be about 

 124 feet in thickness, and are generally overlaid, as more 

 recently observed by Mr. Montgomery, by a thin band 

 or layer of volcanic ash or tuff, which he describes as 

 being very hard, full of small glittering granules of 

 glassy quartz, felspar crystals common, also fragments 

 of various rocks. It decomposes into a yellowish-brown 

 clayey stone, which still shows the glassy quartz 

 granules very distinctly. As the whole of the beds of 

 the cliff have a distinct uniform dip of about 1 in 15 in 

 a direction south by east (S. 28° E.), this band, traceable 

 at sea-level to the north, may be followed in the same 

 position, continuously, to the higher surface north and 

 west, where at a height of 185 feet, near the cliff top, 

 and at the head of a deep gully or arm of the sea, it may 

 be again observed in a more or less decomposed state. 

 Mr. Montgomery draws particular attention to the 

 position and peculiar character of this band, as he is of 

 opinion it may serye as a valuable datum line by which 



