9 6 



NORTH AMERICAN INDEX FOSSILS. 



XLIV. Halysites Fisher. 



Corallum composed of cylindrical or compressed corallites, which 

 are joined into intersecting and anastomosing laminae of single 

 layers of tubes united along the whole of their adjoining side. 







Fig. 153. Halysites calenulatus (N. Y. Geol. Surv.). 



The tubes are covered by a continuous peritheca on their free 

 sides. No mural pores ; tabulae well developed; septa obsolete or 

 in cycles of 12. Ord.-Sil. 



124. H. catenulatus (Linn.). (Fig. 153.) (Ord.) to Siluric. 

 Tubes oval in section united by their narrower sides, or with a 



minute closely tabulate tube intervening. 

 Epitheca with fine and occasionally coarse 

 lines of growth; meshes formed by tubes, 

 large, irregular and varying in size. 



In theOrdovicic beds of Anticosti, Wiscon- 

 sin, Colorado, but especially in the Middle Silu- 

 ric of Europe and North America generally. 



Octameral Corals. 

 XLV. Lyellia E. & H. 

 Coral head consisting of numerous cylin- 

 drical tubes, growing parallel and united by 

 vesicular ccenenchyma, septa 12, short, tabulae 

 irregular. Siluric. 



125. L. americana E. & H. (Figs. 154-155.) Siluric. 

 Tubes \y 2 to 2 mm. in diameter, separated by two tube-diam- 

 eters or something less. Septa comparatively short, coenenchyma 

 of fine cysts. 



FlG. 154. Lyellia am- 

 ericana, vertical and 

 transverse sections en- 

 larged (after Lambe). 



