C. B. Davenport 



11 



second class includes chiefly empty shells, whose inhabitants have perhaps met with a 

 violent death through predaceous animals, or the smothering of a stirred up muddy 

 bottom, 2 also the dead bodies of Crustacea, such as Limulus. This debris is piled up 

 at the lower edge of the middle beach and is renewed twice a day. Especially, how- 

 ever, after a storm is the accumulation large. At such times and at certain seasons of 

 the year one may meet with particular species in large numbers. Thus, early in Sep- 

 tember, 1901, as the young Pectens were swimming into the inner harbor, a combina- 



FiG. 5. — Photograph of north side of sand spit, near the western end, at low tide. In the central foreground is the 

 high-tide line, marked by a mass of debris. On the left is the gravelly lower beach; the middle beach and storm 

 bluff are at the right. 



tion of high tide and sea breeze left thousands of them stranded on the upper and 

 even on the lower beach. 3 The drowned insects are largely leaf eaters (Chrysome- 

 lidse, including the Colorado potato beetle) and, especially in the early summer, lady- 

 birds (Coccinellidae) of various species. All of these constitute a rich, frequently 

 replenished food supply, the only disadvantage connected with it being the dangerous 

 proximity of the sea, with its occasional very high tides and its storm-born breakers. 

 As could have been anticipated, certain animals have come together to make use of 

 this food material. Some are herbivorous, others are scavengers, and others still are 

 predaceous. 



2 In March, 1890, the levee gave way on the left bank of 

 the Mississippi river above New Orleans. The waters 

 pouring through Lake Ponchartrain into western Missis- 

 sippi Sound so stirred up the muddy bottom that the great 

 beds of oysters of this region were killed. (Smith, 1894.) 



3 During a visit to Santa Rosa island, outside of Pensa- 

 cola Bay, Florida, in March, 1902, 1 found the beach cov- 

 ered with thousands of Portuguese men-of-war (Physalia), 

 and the floating gastropod, Janthina fragilis, thrown up 

 by the southerly storms. 



165 



