GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 433 



a genus, designating as the type-species 0. plana M. Edwards and 

 Haime, which is a new name for Agaricia sommeringii Michelin * 

 (not Goldfuss), from the middle Oolite of Mecrin and Hannonville 

 (Meuse) . A part of the description of 0. plana is as follows : ' ' Quelques 

 colhnes minces et peu saillantes entre lesquelles on voit souvent 

 plusieurs series de centres calicinaux. Ceux-ci sont bien distincts et 

 peu profonds." 



The multiple series of calices between collines and the very dis- 

 tinct calicinal centers appear to be valid generic differences. Further- 

 more in the distinct calices of Pironastraea the columella is false but 

 clearly papillary, whereas in Oroseris the columella is rudimentary. 

 There may be additional differences in septal structure not ascertain- 

 able from the short description of the type-species of Oroseris. 



Pironastraea differs from Pachyseris by its more distinct calicinal 

 centers; but apparently it is the ancestor of the ] atter genus. 



PIRONASTRAEA ANGUILLENSIS, new species. 



Plate 111, figs. 1, la, lb; plate 112, figs. 1, la. 



Corallum forming plates as much as nearly 5 cm. thick, and more 

 than 12 cm. across. Width of valleys measured between collines 

 summits from 2.5 to 5.5 mm., about 4 mm. usual; height of collines 

 above the bottom of the axial furrow or of the columella pit about 

 3 mm. Distance between distinct calicinal centers ranges from 3 

 to 4 mm. 



Septa numerous, from 38 to 45 in fully developed calices, most of 

 them extend to the axis, some grouping in 3's at the calicular ends. 

 On a septum 2 mm. long about 10 crowded, knot like dentations. 

 Septo-costae equal, crowded, 18 were counted within 5 mm. 



The columella fossa, where the calicinal centers are distinct, is a 

 small pit, less than 0.5 mm. in diameter. 



Synapticulae abundant, crowded, 7 or more to an interseptal 

 loculus. 



Locality and occurrence. — Anguilla, stations 6893, 6894, 6966, 

 Crocus Bay, T. W. Vaughan collector. A specimen from station 

 6966 was obtained in place between 30 and 50 feet above the base 

 of the bluff on the west side of Crocus Bay. 



Porto Kico, Lares Road, zone C, collected by Mr. Bela Hubbard 

 of the New York Academy of Sciences Porto Rico Expedition. 



Type.— No. 325174, U.S.N.M., pi. Ill, figs. 1, la, 16. 



Paratype.—No. 325175 U.S.N.M., pi. 112, figs. 1, la. 



i Iconograph zoophytol., p. 105, pi. 23, fig. 2, 1843. 



