478 BULLETIN" 103, UNITED STATES NATIONAL MUSEUM. 



but the transverse views of the corallites are very distinct. Coral- 

 lites one-third inch [8.3 mm.] in diameter, not crowded. Septa in 

 six systems, two cycles in four systems and three in the other two. 

 The tertiary orders are small, and often join the secondary near the 

 columella. The primary septa are square and large at the wall, and 

 not very linear, but staff-shaped within; their width at the margin is 

 ■one-fifteenth [1.7 mm.] inch. The secondary septa are very much 

 smaller and thinner than the primary, but nearly as large when the 

 tertiary orders are present. Costae wide apart. Exothecal cells 

 scalariform, wider than high; from one-thirtieth to one-sixtieth 

 [0.8 to 0.4 mm.] inch high, and one-fifteenth inch [1.7 mm.] long. 

 Endotheca abundant. 



"This form has squarer headed septa, longer exothecal cells, costae 

 wider apart, and a lower septal number than many of the forms of 

 the species ; and differs from the forms with three more or less incom- 

 plete septal cycles in the greater thickness of the inner part of the 

 septal laminae, the broad exothecal cells, and in the disposition of the 

 tertiary septa to join the secondary." 



The original description of var. minor is as follows: 



"Corallites tall, slender, crowded, distinct; walls circular, not thick. 

 Calices circular, somewhat variable in size; the largest is three-tenths 

 inch [7.5 mm.] in diameter. The larger septa are spear-shaped, the 

 smaller linear ; they are in six systems of two cycles ; rarely three cycles 

 in two systems in some corallites. Primary septa much larger than 

 the secondary, but nearly equaling them when there is a third cycle. 

 Columella large. 



"The alternate large and small, spear-shaped and linear septa are 

 very well seen in this form. The same details as in this form are 

 found in several specimens with larger corallites." 



It seems to me that varieties nugenti and minor should not be sepa- 

 jated, and I am using nugenti as the varietal name. This variety is 

 principally characterized by its small (diameter about 7 mm.) and 

 relatively distant calices. The specimen represented by plate 138, 

 figures 3, 3a, apparently has more compact structures than specimens 

 more typical of the species. The compact appearance I believe is in 

 large part due to secondary mineral changes, and to the surface having 

 been worn, for some septal perforations are recognizable and synap- 

 ticulae are distinct. An unfigured specimen referred to var. nugenti 

 has perforate corallite walls and perforate septa, but the septa of a 

 worn lateral corallite are mostly solid. As it is usual for the skeletal 

 structures of stunted corals to be denser than those of specimens 

 living under more favorable conditions, it is probable that nugenti is 

 only a vegetational variant of typical D. crassolamellata. 



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

 mation at station 6881, Willoughby Bay (figured specimen), and 6854, 

 Rifle Butts, collected by T. W. Vaughan. 



