388 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



four complete cycles; the fourth and fifth orders often curve toward 

 the third order. Lamellae rather cribriform, joining the columella 

 by oblique processes. Columella lax, small, and formed by dissepi- 

 ments from the septa and a central spongy mass. Endotheca very 

 abundant, vesicular, and horizontal, with four or five dissepiments 

 in one-tenth inch [2.5 mm.]. Exotheca abundant, nearly equal to 

 the endotheca. Reproduction by extra-calicular budding. Diam- 

 eter of the corallites from three-tenths to seven-twentieths inch [7.5 

 to 8.25 mm.]. 



"This species is closely allied to the astraeans with great endo- 

 thecal development, and especially to Astraea vesiculosa Edwards 

 and Haime, from Dax, as well as to .A. antillarum nob., and A. 

 endothecata nob." 



Locality. — "The Marl of Antigua." 



Illustrations based on one of Duncan's original specimens, but not 

 the type, are given on plate 91, figures 1, la-. 



This species is represented in the Antigua formation of Antigua, 

 the Pepino formation of Porto Rico, the Culebra formation of the 

 Canal Zone, and in the marls and limestone of Anguilla. The prin- 

 cipal variation consists in the size of the calices. The minimum size 

 of the calices in the Antiguan specimens (pi. 91, figs. 2, 3, 3a) is 

 about 7 mm., which is about the average for the Porto Rican speci- 

 mens (pi. 92, fig. 1), and the calices of the specimens from the Canal 

 Zone (pi. 92, fig. 2) average slightly smaller than those from Porto 

 Rico, but the two sets of specimens differ very little. In Anguilla 

 (pi. 92, fig. 3; pi. 93, figs. 1, la) the large and small calicled forms are 

 found in association. 



The amount of the protuberance of the corallites varies greatly, 

 but protuberant and low corallites are found on the same corallum. 

 Usually where the corallites are low the alternation in size of the 

 costae is not so pronounced as where the corallites are exsert; but 

 some protuberant corallites of the specimen represented by plate 92, 

 figure 3, have equal costae on at least one side. 



There are pali before all except the last cycle of septa; they are 

 moderately wide, erect, rounded above, form two crowns. 



Localities and geologic occurrence. — Antigua, in the Antigua forma- 

 tion, at station 6881, Willoughby Bay, collected by T. W. Vaughan. 



Porto Rico, in the Pepino formation, station 3191, 4 miles west of 

 Lares, collected by R. T. Hill. 



Canal Zone, in the Culebra formation, at station 6020c Las Cascadas, 

 collected by Vaughan and MacDonald. 



Anguilla, stations 6893, 6894, 6966, in the lower and the middle 

 beds on the south and west sides of Crocus Bay; 6969a, bottom bed 

 at Road Bay. 



