0. costata -14- 
their has© la narrower than that of the oostae. They are arranged 
in 3ix systems, the cycles being very irregular. In three 
systems there are three cycles, and in the rest an incomplete 
fourth; rarely there are two systems with four complete cycles; 
the fourth and fifth orders often curve towards the third order. 
Lamellae rather cribriform, joining the columella by oblique 
processes. Columella lax, small, and formed by dissepiments 
from the septa and a central spongy mass. Bndotheca very 
abundant, vesicular, and horizontal, with four or five dissepi- 
ments in l/lO inch. Exotheca abundant, nearly equal to the 
endotheca. Reproduction by ext r a- call cular budding. Diameter 
of the corallites from 3/l0 to ?/20 inch. 
This species is closely allied to the Astraeans with great 
endothecal development, and especially to Astraea vesiculosa , 
Edwards and Haime , from Dax, as well as to A. Antillarum , nob., 
and A. en do the cat a , nob. " 
Local ity ; T&e marl of Antigua. 
Remar ks: The relations of _0. costata to £. cavernosa have al- 
ready been considered in discussing the synonymy and variation of that 
species. 
