128 



Genus ZAPHRENTIS. Rafinesque. 



[Ety. : Za, very; p/nr nt is, iliaphragm.] 

 (An. Des. 8ci. Phys. Briix., Vol. V., p. 234.) 



rorallum simple, conical oi- turl)inate, or conico-cvliu- 

 clrical, with a deep calyx, and well-developed sejita, the 

 primary ones reaching to the center. Dissepiments and 

 tabulae occur, the latter usually well developed. A deep 

 fossula marks the abortion of one of the four ])rimnry 

 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. 



Z.\PHREXTIS SIMPLEX. Hall. (Fig- •!•) 



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



Distinguishing Cliaracters. — Smooth and 

 gently curving, regularly tapering outline, 

 often abruptly defiected at the base; septa 

 scarcely reaching the center: taljulae strong, 

 curving down near the margin ; disse|)iments 

 few. 



Found in the coral layer of the lower Mos- j^. ^ zaj,hrentis 

 cow shales, at Section •") ; also in the Encri- '■""^'''■•' '•^^"^ ^ ^■ 

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



Gexis am plexus. Sowekhy. 



[Ety.: Ample.fi/s. encircling.] 

 ( Minenil 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^, frecpiently l)ent 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 tabube in 

 the absence of the septa. 



