378 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



jacobiana Vaughan, indicate similarity in horizon with zone D of the 

 Rio Gurabo section . 



3. ORBICELLA IMPERATORIS, new species. 



Plate 86, figs. 2, 3, 4, 5. 



Corallum forming rounded masses 16 cm. or more in diameter. 



Calices in the type-specimen are not much elevated but have a dis- 

 tinct, somewhat raised wall; in other specimens the corallites may 

 project as much as 2.5 to 3 mm. Calicular diameter, 3.5 to 5 mm.; 

 distance between calices, from 2 to 3.5 mm. Corallites joined by 

 prominent, rather thin, distant costae, which correspond either to 

 all cycles of septa or to the primaries and secondaries . 



Septa, typically in three complete cycles; the 6 primaries promi- 

 nent, thicker than the members of the higher cycles, and extend 

 to the columella; the secondaries usually do not reach the columella, 

 only about half as long as the primaries; tertiaries shorter and thin- 

 ner than the secondaries. The septa are usually distant in the wall. 

 The third cycle of septa is incomplete in some calices ; while in large 

 calices a few secondaries may reach oi almost reach the columella. 



Columella formed by the fusion of the inner edges of the primary 

 septa. 



Endotheca well developed as dissepiments. Exotheca well devel- 

 oped between the strong costae, about 3 dissepiments within 1.5 mm. 



Localities and geologic occurrence. — -Canal Zone, Panama, in the 

 Emperador limestone, at stations 6015 and 6016, quarries in Empire, 

 and 6017, one mile from Empire toward Las Cascadas, collected by 

 T. W. Vaughan and D. F. MacDonald; station 6256, in the Emperador 

 limestone, 1% miles south of Miraflores, collected by D. F. MacDonald. 



Cuba, station 3450, 4 miles north of the City of Pinar del 

 Rio, and station 3451, one-half mile west of Cienaga railroad station, 

 near Habana, collected by T. W. Vaughan; station 3566, Bejucal, 

 collected by Arthur C. Spencer; station 7544, Rio Yateras, near 

 Guantanamo, collected by O. E. Meinzer. N. H. Darton, collected 

 at station 7664, on the north slope of La Piedra, northeast of Jamaica, 

 which is northeast of Guantanamo, a specimen of OrbiceUa apparently 

 referable to this species. The calices are rather large, 7 mm. in 

 diameter, and nearly all of the secondary septa reach the columella. 

 It seems very near 0. antillarum. The specimens from Cienaga, 

 Cuba (pi. 86, fig. 5), is illustrated as well as the cotypes from Panama. 



Anguilla, stations 6893 and 6967, Crocus Bay, collected by 

 T. W. Vaughan. 



Cotypes.— No. 324884, 324902, 324903, U. S. N. M. 



Paratope.— No. 324878, U. S. N. M. 



This species is distinguished by the small size of its calices, its 

 prominent costae, its 6 long septa, with intermediate septa shorter 

 according to cycle. 



