Those of the first cycle alone are large and conspicuous; they are a little exsert, a little 

 unequal in size, and they descend straight to the very bottom of the cup, where they meet. 

 Corallum snow-white, the pedicle with a faint cinnamon-brown suffusion. 



Greatest heigfht of corallum iS millim. 

 Major diameter of calicle 8 „ 



Minor „ „ 7 • » 



The characteristic feature of the corallum of this species is the burial of the septa of 

 the 3 rd and 4 !h cyclcs in the depths of the cup where at first they escape notice. lts nearest 

 relative seems to be D. simplex Verrill (American Journal of Science and Arts, 1870, p. 371) 

 from the West Indies. 



XVIII. Flabellum Lesson, E. & H., Duncan. 



The identification of the species of this genus presents difficulties which, in the absence 

 of actual types for comparison, are insuperable ; tor many of the species are not only highly 

 variable, but they also undergo radical changes of form in the course of growth, these changes 

 affecting the shape of the corallum, the form and size of the columella, and the number of the 

 septa. Xo one can be more dissatisfied than I am myself with the present attempt to determine 

 the large number of forms collected by the "Siboga". 



Synopsis of the Siboga Deep-sca species of Flabellum. 



Corallum free or becoming so: — 



I. Corallum shaped like a fully-open fan : — 



1. Septa in six or more cycles: — 



I. The larger septa form 48 compartments each of which 

 contains 3 smaller septa: the circumference of the 



corallum is less than a semicircle \. F. distinctum. 



II. The larger septa form 48 compartments each of which 

 contains 7 smaller septa: the circumference of the 

 corallum is much more than a semicircle . ... 2. F. lamellulosum. . 



2. Septa in 5 cycles, the last cycle incomplete : lip of calicle 



jagged 3. F. laciniatum var. 



II. Corallum shaped like a nearly-open fan: septa in 5 complete cycles: 



lip of calicle jagged 4. F. suluense. 



III. Corallum either a half-open fan, or a compressed conc : — 



1. Septa in six or more cycles: — 



I. Lateral costaï sharp or jagged 5. F. australe. 



II. No lateral costa; 6. F. latnm. 



2. Septa in fïve cycles, the fifth cycle incomplete; lateral costa? 



sometimes spinose 7. F. irregulare. 



3. Septa in four cycles : no lateral costae 8. F. dens. 



IV. Corallum an open oval cup: septa in five cycles, with the inferior 



cycles incomplete 9. F. japonicum. 





