, 9 o DISCOVERY REPORTS 



initial letter, and the types within the groups by the addition of a numeral to the initial 

 (e.g. A 4 ). 



The types are described by their composition and colour and to a less degree by their 

 texture, but identification of the minerals composing them has not been attempted. The 

 description does not in all cases correspond with that given in the station list and noted 

 at the time that the station sounding was made. This is largely due to the fact that the 

 samples change colour, many of them considerably, in drying. Samples that are light 

 greenish grey for example when dry appear dark grey, almost black, when wet ; others 

 change similarly. 



The groups are sharply defined from each other and the allotment of any given sample 

 to its group is obvious. The types within the groups, however, are -not in all cases so 

 easily separated and tend to merge into one another through intermediate types. A 

 strong family resemblance running through all the groups with the exception of group A, 

 and occurring in nearly all samples, is the green colour of the silt. This varies from 

 brownish and greyish green, through dark and light greens to yellowish green. It 

 appears, in many instances at least, to be due to a glauconitic substance: glauconite has 

 been identified by Macfadyen (1933) in some samples of bottom deposits from the 

 Burdwood Bank. 



Groups recognized: 



Group A. Chief components, shell and coral fragments. Contains five types: 

 samples from eight stations. 



Group B. Chief component, white or yellowish-white sand. Contains four types. 

 Samples from ten stations. 



Group C. Chief component, brown sand. Contains seven types. Samples from 

 twenty-six stations. 



Group D. Chief component, greyish-brown sand. Contains five types. Samples 

 from twenty-six stations. 



Group E. Chief component, grey sand and silt. Contains four types. Samples from 

 fifteen stations. 



Group F. Chief components, green or greyish-green sand and silt. Contains four 

 types. Samples from twenty-six stations. 



DESCRIPTION OF THE TYPES 

 GROUP A. SHELL AND CORAL FRAGMENTS 



Type A 1 . Medium grades consist of fragments of coral (Turbinolidae) with a smaller proportion 

 of clear angular sand grains, shell fragments and grey gravel. Silt yellow, appearing to consist of 

 coral detritus. Two samples, WS 93, WS 802. 



Type A 2. Medium grades consist of coral and shell fragments with dark grey gravel. Large 

 dark grey pebbles and echinoderm spines in the coarser grades. Fine sand and silt yellow, con- 

 sisting of coral and shell detritus. One sample, WS 86. 



Type A3. Medium grades consist of coral and shell fragments; a large proportion of whole and 

 broken bivalve shells (Pecten and clam types), dark grey pebbles and gravel in the coarser grades. 



