NOs. b7, SMITHSONIAN EXPLORATIONS, IQIO 28 
was bodily quarried out of the bank, and these strata with their 
contained corals were later set up in the exhibition hall of 
paleontology. 
The lowest layer of limestone (A) is composed largely of fossil 
brachiopod shells. Next above is a layer with scattered corals (B) 
belonging to a long-tubed species (Colummnaria calicina Nicholson), 
probably torn by waves from a nearby coral reef. Overlying this 
is a limestone stratum (C) largely made of the twiglike stems of 
stony Bryozoa ( Trepostomata ). 
Fic. 27—Trenton limestone outcrop near Lexington, Ky., with one stratum 
containing large heads of coral (Y). Photograph by Bassler. 
The main reef of corals (D) is chiefly composed of the rounded 
heads of three species of honey-comb corals, some with radial parti- 
tions in the tubes (Columnaria alveolata Goldfuss), others without 
such partitions (Columnaria vacua Foerste), and still others with 
spongy walls (Calapoecia cribriformis Nicholson). Large stems of 
fluted or nodular Hydrozoa (Beatricea) are scattered among the 
honey-comb coral masses. 
Horn corals (Streptelasma rusticum Billings) are to be seen in 
both the lower and upper coral beds. The spaces between the lime- 
