182 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



rocks the island must have been situated in a deep sea ; and the fine- 

 grained beds could then have been produced from an admixture of 

 the rock composing the island, or of a rock somewhat similar 

 in character. These rocks are not seen in contact veith the island 

 at all places ; but there is evidence to shovr that they have been 

 faulted downwards at these parts. I am not quite satisfied that 

 there is not a break here in the strata ; for though the strike is 

 nearly the same as in that of the overlying beds, yet there does 

 not appear to be true conform ability. 



3. Conglomerate composed of quartz pebbles, with a purplish 

 matrix, indicating a shore-deposit. Masses of rock similar to the 

 green beds of the island are also present ; and the whole might easily 

 have been formed out of parts similar to portions of the island now 

 visible. The purplish colour could easily arise out of the green under 

 another state of oxidation of the iron ; for the frequent alterations 

 shown in these lower rocks from purple to green and red, even in 

 the same bed, make this matter of colour of little importance. 



4. Greenish micaceous sandstones, with ripple-markings on the 

 surface, and indicating shallow-water or shore-deposits. Worm- 

 burrows and holes are common in these sandstones ; and at pre- 

 sent they are the only indications found of the existence of life at 

 this period. 



5. Finer-grained red flaggy beds, sometimes, however, of a bright 

 green colour. Here we have plentiful indications of the presence of 

 animal remains. These beds were apparently deposited in mode- 

 rately shallow water not far from shore. Brachiopods are abun- 

 dant, as also some small bivalved crustaceans. Some fragments of 

 a trilobite also have been discovered in these beds. 



6. A great thickness of purj)le and green sandstones and grits, with 

 the surface of the beds frequently ripple-marked. These were evi- 

 dently dejDosited in shallow water, or formed a sea-beach. The only 

 evidence of animal life found at present in these beds consists of 

 worm-burrows and holes, which occur very generally throughout the 

 whole series, 



7. A varying series of beds, at first gritty and of a yellowish co- 

 lour, with also some fine conglomerate, then greenish and of finer 

 grain, and afterwards red and purple sandstones. The finer beds 

 here, as before, yield the greatest number of fossils and the greatest 

 variety of forms. Between the grit-beds in the fijst part of this 

 series there are some thin bands of very fine shale, which must have 

 been made up of a muddy deposit, probably washed down by a river ; 

 and on these we have those markings figured in pi, xvi, vol. xxvii, of 

 the Quart. Journ.Geol. Soc. which I have n&xned Protospongia? major. 

 It is really doubtful at present what these are ; and I am sorry the 

 figures do not quite show their true character, as, instead of being 

 simple lines, they should indicate flattened fibres, as described in the 

 same paper, p. 401. Possibly they are impressions of the fibres of 

 sea-weed only ; whilst, on the other hand, there are some facts, such 

 as the thinness of the bands frequently interstratifying very rough 

 grit, to indicate a possibility of their being brought down by a river 



