34 PEOr. T. W. E. DAVID & MR. E. F. PITTMAN [Feb. 1 899, 



An ocbreous-brown soft rock containing radiolaria as casts and also 

 with the test preserved. Some of these are translucent, others, 

 occur as opaque ochieous casts in an ochreous base ; v^hile others 

 have a distinct bluish- grey coloration. 



In size they vary from 0-083 to 0*31 mm. Eadiolaria are present 

 at the rate of at least 50 to 60 in a field having a diameter of 

 3-1 mm. The particles composing the base are very fine-grained, 

 about 0*05 to 0-063 mm. in diameter. 



Slide No. 62S. — From a quarry west of the serpentine-dyke 

 north of Patterson's house, Tamworth. Rock somewhat similar to 

 the preceding, but showing one very sharply- defined lamina of depo- 

 sition 1 mm. thick, a dark grey layer with small radiolaria in the midst 

 of a translucent yellowish-grey base crowded with radiolaria, mostly 

 of larger size than those in the dark lamina. The greater number of 

 the particles in the dark lamina are less than 0-025 mm. in diameter. 

 Eadiolaria are present at the rate of at least 100 in a field 3-1 mm. 

 in diameter. Carbonaceous streaks and spots are scattered through- 

 out the base. By transmitted light the radiolaria are either of a 

 semi-opaque pale bluish-grey, or sub-translucent yellowish-grey. 

 By reflected light the former appear opaque milk-white, and some 

 of the latter ochreous. It may be noted that this rock is quite 

 soft, and can be cut with a penknife despite the abundance of 

 radiolaria in it, which are almost, if not quite, as numerous as 

 those in the black cherts. 



Slide No. 386 (9). — Tamworth Temporary Common. A cal- 

 careous dark bluish-grey rock, with obscure casts of radiolaria. The 

 base is chiefly calcareous, with numerous translucent bodies from 0-25 

 to 0-5 mm. in length, and 0-05 to 0-025 mm. in width, showing a 

 loose felted structure like the felspars in a basalt, though not so 

 closely packed together. Most of these are calcareous, and some seem 

 to be films filling irregular cracks in the groundmass. The base is 

 stippled with brown dots and splashes due to limunite, probably 

 pseudomorphous after pyrites. The whole rock, as regards structure, 

 rather resembles a fine-grained basalt. 



Slide of Hack chert, Tamivorth Common ; taken from near 

 radiolarian limestone No. 1. The base is very fine-grained and 

 rather opaque, brownish-grey by reflected light, with numerous 

 black streaks of carbon. Radiolaria are present at the rate of 

 about 100, more or less, in a field 3-1 mm. in diameter. They 

 are preserved in chalcedonic quartz, and in a few cases an internal 

 cast of the medullary test has been retained, showing as an opaque 

 yellowish sphere surrounded by a wide zone of chalcedony, which 

 in turn is enclosed by the broken-down remains of the cortical 

 test. The base appears to be chiefly formed of the comminuted 

 remains of radiolarian tests. 



{b) Tuff-rocks, etc. 



Slide No. 249 (A. 1). — The rock in this slide consists of a base 

 chiefly made up of calcium carbonate, with numerous small fragments 



