484 EUGENE WESLEY SHAW 



Shore features were generally poorly developed, though 12-15 

 miles northeast of Madisonville, Kentucky, 60 miles by water from 

 the Ohio River, there are beautifully developed and well-preserved 

 beach-ridges. These ridges are very symmetrical, being 20-50 

 feet wide, and 8 to 10 feet high (see Fig. 2). They are composed 

 of sand and fine gravel and are situated across the mouths of 

 small tributary valleys. The reason for the excellent development 

 of gravel ridges at this place is the generous available supply of 

 loosely cemented conglomerate, probably Late Tertiary in age, com- 

 posed largely of well-rounded quartz and flint pebbles. Elsewhere 

 there was not a large amount of well-rounded pebbles within 

 reach of the lake and so far no other well-developed ridges have 

 been found. At numerous places where the bank of the lake was 

 easily eroded there is some suggestion of wave cutting, but the 

 evidence has been almost obliterated by recent erosion. One 

 reason for the general poor development of shore features is that 

 owing to the rise and fall of the rivers the lakes were continually 

 fluctuating and were intermittent for a part of the period of their 

 existence. Thus, particularly in districts of low relief, the shores 

 of the lakes did not stand in one position long enough to develop 

 shore features. 



Good collections of fossils were obtained, the fauna consisting 

 of nearly a score of species of gastropods and lamellibranches, and 

 undoubtedly many more species, including perhaps vertebrate and 

 plant remains, might be found. Most of the forms collected inhabit 

 lagoons and the quiet parts of streams. One of them (Campe- 

 loma) is a scavenger living in decaying animal matter. Others 

 frequent lily ponds. Some, such as Vertigo, are northern forms, 

 being found at present from Wisconsin northward. 



The lime masses are probably secretions of blue-green algae, 

 though at present they show little organic structure. They are 

 more abundant in the thinner parts of the formation, and this may 

 be correlated with the fact that lime-secreting algae flourish in 

 very shallow or intermittent waters. 



Previous work. — -Bodies of this clay have been regarded as glacial 

 drift; a lowland phase of the loess; an old normal flood-plain 

 deposit; a back-water deposit from glacial floods on the larger 



