Dec. 1861.] 



Narrikal or Cochin Mud Bank. 265 



lence that would destroy such delicate structures, I allowed it to 

 soak for twenty-four hours. On shaking it up at the expiration 

 of that time I found that at least half of it could not be separated 

 in that way, E therefore pressed it gently with a glass rod ; it 

 resisted the pressure, much in the way that a stiff piece of jelly 

 would do, exhibiting considerable elasticity as well as tenacity, 

 and it is doubtless these properties that enable it to break the 

 force of the waves : — acting like an immense spring, it yields to 

 their pressure, but in the encounter the water loses its force and 

 becomes quiescent, while the mud gently expanding again is ready 

 for a fresh encounter. 



When by a good deal of gentle coaxing, it was diffused in the 

 water, it was stirred well in about five inches of water and allowed 

 to stand for half a minute, when all but the last half inch was 

 poured into another beaker and time allowed for both to subside. 



The first vessel produced some Foraminifera which I refer to 

 the Genus Rotalina, (D'Orbigny) but doubtfully, as no monograph 

 of the Foraminifera is at present accessible and other works in 

 my possession do not give sufficient information to enable me to 

 speak positively. Besides the Foraminifera there were one or 

 two small pieces of larger shells and some very small angular 

 fragments of quartz. 



As much of the water as could be was poured from the second 

 vessel and replaced by strong muriatic acid ; this was kept boil- 

 ing for about three hours, when, after having been allowed to 

 settle, the acid was poured off and an equal quantity of nitric acid 

 added which was kept boiling for about the same time. But as 

 this did not appear to have entirely destroyed the organic matter 

 the deposit was further boiled for four hours in strong sulphuric 

 acid, after which it was washed in several changes of distilled 

 water. There remained, in about equal proportions, Diatomaceae 

 and some amorphous matter which having resisted all the boiling 

 in acids is probably siliceous. 



The following is a list of the Diatomaceae found in this depo- 

 sit ; — they are arranged in the order observed in the last Edition 

 of Pritchard's Infusoria, which contains the most complete 



