CHAPTER Y. 



HYDRAZOIDS AND CORALS. 



Stromatopora expansa Hall and Whitfield. 



Stromatopora expansa Hall and Whitfield, 1873: New York State Cab. 

 Nat. Hist., 23rd Kept., p. 226, pi. ix, fig. 1. 



Growths irregnlar, somewhat spheroidal, made up of nu- 

 merous thin, closely arranged concentric shells, which have a 

 well defined fibrous structure and are perforated by minute 

 pores. 



Sorizon and Localities. — Devonian, Callaway limestone : 

 Winfield (Lincoln county). 



Kone of the species thus far found preserve the minute 

 structure sufficiently well for satisfactory microscopic examina- 

 tion. The zoological affinities of the group are little under- 

 stood as yet, while the objects referred to the genus have 

 comprised a heterogeneous mixture — poorly preserved fossils, 

 having no relation whatever to this group, or even concretion- 

 ary structures. 



Acervularia davidsoni Edwards & Haime. 



Acervularia davidsoni^d'wSir68 & Haime, 1851: Monog. des Polyp. Foss. 



d. Terr. False., p. 318, pi. ix, figs. 4-43. 

 Acervularia davidsoni ^&\\, 1858: Geology Iowa, vol. I, p. 476, pi. 1, figs. 



Sa-b. 

 Acervularia davidsoni Wi(ih.o\^on ^ 1875 : Geol. Sur. Ohio, vol. II, p. 240. 

 Cyathophyllum davidsoni Rominger, 1876 : Geol. Sur, Michigan, vol. Ill, 



p. 107, pi. xxxvii, fig. 4. 



Corallum large, lenticular, composed of polygonal coral- 

 lites, which are seldom of the same size ; lower surface covered 

 by a rather thick, wrinkled, epithecal crust. Corallites with 

 the walls more or less distinctly zigzag in cross-section ; the 

 interior wall not well defined. Septa about 40 in number, with 

 serrated margins. 



