Guppy Reprint 



i73 



sediment underlying the tenacious clay of the bars." 



The material of this mud-lump (which may he called the 

 "Despatch Reef Mudlump"), for samples of which I am indebted 

 to Mr. John Wilson, is of very various degrees of consistency, 

 hardness and fineness of component parts. It contains a large 

 quantity of sulphuret of iron and a few pieces of lignite. Beds 

 of clastic matter varying from small pebbles to find sand indicate 

 estuarine beaches and these are derived from the degradation of 

 tertiary and cretaceous rocks, but there is nothing to indicate the 



Page 29 



existence of deep-sea deposits. In the softer material, a very im- 

 pure gra} r ooze or clay, I have found two or three Foraminifera, 

 for example, Cyclamina cancelata and Amodiscus incertus, but 

 their condition shows that they have been derived from older beds 

 and they are not characteristic of deep water. 



The sunken valleys of the Bocas Region are wortrry of notice 

 and they show how much the interest of the traveller in what he 

 sees would be increased by a slight acquaintance with geology. 

 We have in this region almost ever) T kind of sunken or submerged 

 valle}^. First we have the submerged valley which has been en- 

 larged to several times its original width by the rapid tidal cur- 

 rents running through it. Such are the channels between the 

 Gulf of Paria and the Caribean Sea called the Bocas. Next we 

 have the valley which has been parti} 7 submerged, but which has 

 not been enlarged to an} 7 noticeable extent, because no current 

 runs through it. As an example of this we may take Scotland 

 Bay. On the opposite side of the gulf, that is on the Venezuelan 

 coast, there are several examples of this kind. Teteron is an in- 

 intermediate case between the submerged valley and that which 

 is partly filled up. The valley of Chaguaramas and more notably 

 those of Cuesa and Diego-martin are examples of sunken valleys 

 of which the lower parts have been filled up. 



These phenomena are alluded to in several of my papers (See 

 particularly "Growth of Trinidad" Trans. Canadian Inst. 1904-5. 

 p. 141, &c. Ibid. 1908-9, p. 379.) 



