OYSTER BOTTOMS TN MATAGORDA BAY. 19 



more exposed to the waves, eventually develop into tonguelike 

 ridges at i-i*j,lit angles t<> the general trend of the reef, with muddy 



silted sloughs between them. 



In the discussion thus far, particular consideration has been given 

 to Dog Island Reef, where the conditions are most marked, but the 

 statements will apply with gradually decreasing force to the reef- 

 below. By virtue of its proximity to Dog Island channel, which act- 

 in relation to it much as the Colorado does to Dog Island Reef, 

 Shell Island Reef presents the same characters, though less marked, 

 the upper margin being abrupt, and the spurs and sloughs on the 

 opposite side of the crest being relatively shorter and less differen- 

 tiated. Mad Island Reef being shorter, there is a wider avenue for 

 the passage of currents around its end. The channel at the inner 

 end of Shell Island is not so large, and therefore discharges less 

 water to impinge on the reef below, and finally the water, by the 

 time it reaches this reef, has had an opportunity to deposit no incon- 

 siderable part of its silt, all of which factors still further reduce the 

 formation of spurs on the lower side of the reef. At Half Moon 

 Reef the lower margin is almost entire, but the conditions are still 

 such, by virtue of the preponderating current velocity from the 

 upper bay, that the crest maintains its proximity to the eastern face. 

 and the oysters are better, larger, and more abundant on that side. 

 From Dog Island Reef to Half Moon Reef there is therefore a 

 gradual transition in correspondence with the waning influence of 

 the conditions above indicated. 



SHORT REEFS AND LUMPS. 



The short reefs, or " lumps," as they are usually called, are found 

 principally in the upper part of the bay. though there are a few 

 below Dog Island Reef. They are simply old oyster beds in which 

 the growth is localized, and as a rule they are developed in those 

 places where the currents are less marked than they are below the 

 mouth of the Colorado River. They rise from soft muddy bottoms, 

 which tends to restrict their expansion laterally, and their growth is 

 principally at the top. They often consist of dense bodies of rac- 

 coon oysters. 



FLAT BEDS AM) PATCHES. 



The patches or flat beds are confined to that part of the bay above 

 the vicinity of Dressing Point. They are relatively young, and in 

 many cases their origin can be traced to artificial causes, the culling 

 and throwing overboard of shells and young oysters from boats on 

 their way to market. Many of them formerly produced oysters of 

 excellent quality, and under proper density condition- this phase of 

 their history would undoubtedly be repeated. 



