123 



Genus ZAPHRENTIS. Rafinesque. 



[Ety. : Za, very; phrentia, diaphragm.] 



(An. Des. Sci. Pliys. Brux., Vol. V., p. 234.) 



Corallum simple, conical or turbinate, or conico-cylin- 

 drical, with a deep calyx, and well-developed septa, the 

 primary ones reaching to the center. Dissepiments and 

 tabula? occur, the latter usually well developed. A deep 

 fossula marks the abortion of one of the four primary 

 septa. Costa? and a thin epitheca occur. 



Note.— It is probable that several species of Zaphrentis 

 occur in the Hamilton of this region; only one is here given. 

 however, as definitely identified. 



Zaphrentis simplex. Hall. ( Fig. 4.) 

 (111. Dev. Foss., PL XXI.) 



Distinguishing Characters. — Smooth and 

 gently curving, regularly tapering outline, 

 often abruptly deflected at the base; septa 

 scarcely reaching the center; tabula? strong, 

 curving down near the margin ; dissepiments 

 few. 



Found in the coral layer of the lower Mos- 

 cow shales, at Section 5; also in the Encri- ^^'^ Hal »- 

 nal limestone (?) on the Lake Shore, where it is rare. 



Genus AMPLEXUS. Sowerby. 



[Ety.: Amplexus, encircling.] 

 (Mineral Conchology, Vol. I., p. 165.) 



Corallum simple, conical, or cylindrical, with a well- 

 developed epitheca, and a circular, moderately deep calyx. 

 Septa strong, short, never reaching the center, which is 

 occupied by horizontal tabula?, frequently bent down at the 

 periphery. A well-developed fossula is present. 



This genus differs from Zaphrentis mainly in the smooth 

 central area of the calyx, which is formed by the tabula? in 

 the absence of the septa. 



