CORALS AND BRYOZOA 
OF THE 
LOWER HELDERBERG GROUP. 
DESCRIPTIONS OF SPECIES. 
STREPTELASMA, Hall. 1847. 
Streptelasma strictum. 
PLATE I, FIGS. 1-10. 
Streptelasma ( Petraia ) stricta, Hall. Twenty-sixth Rept. N. Y. State Mus. Nat. Hist., p. 114. 1874. 
“ stricta, Hall. Thirty-second Rept. N. Y. State Mus. Nat Hist., p. 142. 1879. 
“ strictum, PIall. Report of State Geologist for 1882. Expl. pi. 1, figs. 1-10. 1S83. 
Corallum simple, conical, very gradually and regularly enlarging; straight or 
very slightly curved, except at the apex, which is sometimes more abruptly 
bent. Exterior marked with strong undulations of growth and numerous 
fine concentric striae; external rays very prominent, from forty-five to fifty 
at a point where the diameter of the corallum is 15 mm.; the increase 
in number taking place usually at three distinct points, but sometimes at 
only two. 
Calix deep, sides thin and nearly erect; a flat space at the bottom. 
In one calix, having a diameter of 20 mm., there are fifty-four lamellae; 
alternate lamellae extending only a short distance from the walls at the 
base of the calix and frequently coalescing with the primary lamellae. 
