146 DREDGINGS OF THE MARINE BIOLOGICAL ASSOCIATION: 



M. 21g. S. 25° W. Edd., 21-2 miles. 



(Not inserted in the above series because structurally different ; all 

 the above are of ordinary type.) 



A compact rock with granular fracture ; the granules vary from buff 

 to a light brown with a tinge of Indian red. The rock has been bored 

 by molluscs. 



A sandstone cemented by crystalline calcite, dolomite, or in the 

 alternative a very sandy crystalline limestone. The quartz grains well 

 rounded with numerous, and some large, fluid inclusions. One grain 

 which proves to be part of a quartz mosaic contains a fragment of rich 

 brown mica. Yet another grain contains brown mica, and many have 

 acicular microlites, possibly apatite. Considerably less numerous than 

 the quartzes are felspar grains, botli orthoclase and plagioclase. There 

 are numerous fragments of a brown rock, apparently a palagonite, 

 containing some crystals, including mica. The rhombs of dolomite are 

 clearly marked out by concentric bands of dark brown inclusions, 

 grains, and microlites, which tend to form radial bunches. In some 

 cases the centre of a rhomb is completely darkened. 



MARLS. 



Under this heading are included hard marly limestones, those more 

 exceptional forms from the Trias which are calculated to resist abra- 

 sion ; with them is a smaller percentage of the true friable marl. 



M. 34b. S. 28° W. Edd., 18 5 miles. 



A dark red pebble, with smooth surface, much bored by molluscs. 

 A cut surface shows very compact rock, the red colour of which is 

 slightly mottled by a lighter shade. In the section this mottling 

 is much more prominent. The rock is minutely granular, the mineral 

 being probably a mixture of calcite and dolomite. There are also 

 small angular fragments of quartz, and apparently some fibres of 

 gypsum. Some of the borings have been infilled with secondary sand- 

 stone having calcareous cement. The stone is a very hard marl. 



M. 9f. S. 31° W. Edd., 217 miles. 



A fine-grained red marl. 



Much very fine sand, with some larger quartz grains. The colour 

 not uniformly distributed but mottled with grey. Many of the grains 

 appear to be crystalline calcite or dolomite. 



M. 31. S. 25° W. Edd., 15 miles. 



Soft variegated marl, red and green. 



M. 36. S. 37° W. Edd., 17*5 miles. 

 Hard chocolate-coloured marl. 



