0. costata -13- 
Qrhicella costata (Duncan), 
PI. fig. 
1863. Astraea costata , Duncan, Quart. Jour. Geol. Soc. London, 
Vol. XIX, p. 42®, PI. XIII, fig. 9. 
1867. He li aatraea costata , Duncan, Quart. Jour, Geol. Soc. 
London, Vol. XXIV, p. 24. 
Original description: 
"The specimens of this species which I have examined present 
polished longitudinal and transverse sections of corallites, hut 
I have seen no caliees. Corallites long, parallel, sometimes 
deformed, generally circular in transverse outline, not crowded, 
hut close, varying in size, Intercorallite spaces very distinct. 
Walls thin, not thicker than the delicate septa. Costae large 
alternately, hoth sizes equally produced; wedge- spahed at the 
wall, pointed, and often hent at the free end. Septa all deli- 
cate and linear near the columella and in the middle; at the wall 
