396 ME. S. O. EIDLET ON VAEIATION Ilf 



The facts on wMcli I base this argument will be found in the 

 following descriptions of two species' of PTiyllangia. I had been 

 led to examine these species closely for the purpose of identifying 

 some specimens lately added to the national collection ; I found 

 that they were somewhat "critical" species, and that, one of 

 them was incorrectly identified in the collection ; and that, 

 further, certain of the characters on which stress had been pre- 

 viously laid by describers of species proved remarkably unstable. 

 For these reasons I now give descriptions of two series of speci- 

 mens illustrating these two species. 



Phtllangia papuensis, Studer. (Plate XVI. figs, 5-10.) 

 Phyllangia papuensis, Studer, MB. Ak. Berlin, 1877> p- 642. 



The specimens consist of fragments detached from an old anchor 

 at Amboyna by Mr. H. O. Forbes, and presented by him to the 

 British Museum. Studer's description of specimens from the 

 Solomon Islands diflers from them in a few points, viz. the inferior 

 diameter of the calicles (4-5 millim., the largest of the present 

 series examined is 7 millim.), and the "small" paliform lobes. 

 He describes the columella as small, consisting in some cases of 

 only one to three short pillars. 



In the Amboyna specimens the basal stolon is moderately 

 thick, the corallites are 8-9 millim. in greatest height, the pri- 

 mary septa in large calicles rise 1 millim. above the wall of the 

 cup 5 it is the largest calicles which have the thinnest primaries ; 

 septa of a fourth cycle may be present on one side of some systems 

 of a calicle. The central (columellar or pseudo-columellar) mass 

 is usually composed of one roughly pointed, prominent, central 

 column (the columella s. str.), and of six to ten erect similar 

 paliform lobes arising from the inner margins of the primary and 

 some secondary septa, and of subjacent contort, rather coarse 

 trabeculge uniting them to the columella : these trabecules may (i.) 

 either be evident from above, the paliform lobes and columella 

 forming inconspicuous points on their upper margins, or (ii.) these 

 structures may project boldly from the trabeculae, or (iii.) the tra- 

 beculse may be disguised and the spaces between them concealed 

 by the extension between the trabeculge, lobes, and columella of 

 a calcareous lamina, uniting the whole into a dome from which 

 the lobes and columella arise as pinnacles (see figs. 7-9). 



The costge are broad, flat, subequal, and granular, and extend 

 in bold sweeping curves, sometimes rising into quite prominent 



