446 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



the columella and the quaternaries to the tertiaries about halfway 

 between the wall and the columella, or somewhat nearer the columella. 

 At the wall the thickness of the septa and the width of the interseptal 

 loculi are nearly the same, but farther within the calice the septa 

 are thinner and the loculi are wider. 



Next the wall the septal margins are usually flattened from above, 

 producing a Hat area ranging from about 0.5 to about 1 mm. wide, its 

 inner edge marked by a ring of synapticulae, and the wall forms a 

 more or less median slightly raised ridge. From this area the margins 

 slope slightly to the bottom of the calicular fossa. The peripheral 

 flat zone is not present in all calices ; in many there is a gradual slope 

 or a gently convex curve from the wall to the bottom of the calice. 

 On the septal margins are fine, crowded, bluntish dentations, which 

 in many instances are compressed transversely to the septal plane. 

 About 16 were counted on a septum 2 mm. long; 12 were counted 

 on another septum 1.5 mm. long. The number, therefore, is between 

 8. and 9 for a distance of 1 mm. The septal faces are closely beset 

 with blunt granulations. Synapticulae well developed near the wall. 



Columella rather small, with a delicately papillate upper surface 

 in the best-preserved calices. 



This Santo Domingan specimen has greatly puzzled me, perhaps 

 partly because it is immature. The calices are shallow, not having a 

 distinct axial fossa, as in typical S. siderea, and the septal dentations 

 are more numerous than is usual in S. siderea. As the calices of the 

 Bowden specimen are excavated on the top of the corallum and 

 superficial near the lower edge, the shallowness of the calices of the 

 Santo Domingan specimen does not seem a sufficient basis for ref erring- 

 it to a different species. Although the septal dentations are finer than 

 the average in S. siderea, they are not finer than the dentations on the 

 outer prolongations on some of the septa of the specimens represented 

 by plate 35, figures 2, 3, in which there are 8 or 9 fine teeth within 1 

 mm. outside the calicular fossa. For these reasons it seems to me 

 that the Santo Domingan fossil should be referred to S. siderea; 

 and I believe that the coral designated as Siderastraea crenulata 

 var. antillarum 1 by Duncan should also be referred to S. siderea. 

 Duncan says that his variety antillarum is near S. siderea. I ex- 

 amined Duncan's type in the collection of the Geological Society 

 of London. It is a flattened mass, rounded above. Calices irregu- 

 larly polygonal or hexagonal, separated by sharp walls; diameter 

 4 to 5 mm. Septa in four complete cycles, margins beaded. Col- 

 umella papillary, in some calices terminated by several stout knobs. 



Fossil specimens obtained by me at station 3446, in the La Cruz 

 marl, first deep cutting east of La Cruz, near Santiago, Cuba, differ 



i Geol. Soc. London Quart. Journ., vol. 19, p. 435, 1863. 



