ANTHOZOA—TETRACORALLA. 



55 



Fig. 76. a-b, Streptelasma profundum ; c-d, S. corniculum ; e-f, S. rusticum ; g t 

 Enter olasma calicula (Lambe-Contr. Pal.). 



2. S. corniculum Hall. (Fig. 76, c-d.) Middle Ordovicic. 

 Corallum curved, calyx moderate, septa numerous, twisted at 



the center. 



Trenton and Galena limestone, New York, Canada, Iowa 

 Minn., etc. 



3. S. rusticum Billings. (Fig. 76, e-f.) Upper Ordovicic. 



Fig. 77. Streptelasma {Enterolasma') Fig. 78. Stereolasma rectum, {a) car- 

 calicula (N. Y. State Geol. Surv.). dinal and [l?) alar views. 



Larger than preceding (2^-3^ inches), septa coarser and more 

 strongly twisted, forming a vesicular pseudocolumella at the center. 



Lorraine and Richmond beds of Minnesota, Iowa, Indiana, 

 Ohio and Canada. 



