53 



NORTH AMERICAN INDEX FOSSILS. 



II. Z. cliffordana Edwards & Haime. Lower Carbonic. 



Corallum a curved cone, with a deep calyx, the septa of which 



are all nearly equal in strength, becoming thinner towards the cen. 



FiG. 84. H. cah-are 

 forme. Transverse sec 

 tion (Simpson). 



Fig. 83. Hapsiphyl- 

 lum calcareforme (Ind. 

 Geol. Surv. ). 



FlG. 86. Amplexus ham 

 iltonice. 



the side of 



ter. Fossula generally on 

 least curvature. 



In the Kinderhook beds of Illinois, the 

 Chester beds of Ohio, etc. 



12. Z. (Hapsiphyllum) calcareformis 



Fig. 85. Amplexus yan- 

 delli with transverse and lon- 

 gitudinal sections (Lambe 

 Contr. Can. Pal.). 



Hall. (Figs. 83, 84.) Lower Carbonic. 



Small, slender and uniformly tapering, sometimes curved. Fos- 

 sula narrow, outlined by a compressed horseshoe-shaped wall 

 formed of septa united at the center. Shorter septa joining the 

 longer which in turn unite with the wall of the fossula. 



In the St. Louis limestone of Spergen Hill, Lanesville, Indiana, 

 and other localities. 



13. Z. (Hapsiphyllum) spergenensis Worthen. Lower Carbonic. 



Like the preceding, but with two rudimentary pseudofossulae, 

 and short epithecal spines. 



Occurs with the preceding. 



III. Amplexus Sowerby. 

 Generally cylindrical or conico cylindrical corals, with structure 

 much like Zaphrentis but with the septa only reaching a short way 

 out onto the well developed horizontal tabulae. A strong fossula 

 is generally present. Ord. ?-Carb. 



