86 PERCY SLADEN TRUST EXPEDITION 



The stomodseum is much compressed laterally, its long diameter being about 2 mm. 

 Owing to the breadth and thickness of the stomodseal ridges grooves are formed between 

 them. Rod and spindle-shaped nuclei are massed together in the ridges around a some- 

 what granular protoplasmic region* into which slender filaments pass from the mesoglaea ; 

 digestive vacuoles and a few nematocysts III and rarely I also occur. The mesoglsea is 

 thickened, appearing concavo-convex in transverse section. Near the skeletal attach- 

 ments of the mesenteries, the calicoblast is thickened and vacuolated, containing ' ' desmo- 

 cytes " at various stages of development. In the oral-disc and in the outer wall of the 

 edge-zone the ectoderm is thick, with a columnar facies containing a row of transparent 

 oval vacuoles ; nuclei of varying shape occur in the middle of the layer, with nematocysts 

 I and II above. Filaments are present on all the mesenteries, being rudimentary on 

 the narrower subsidiaries ; nematocysts are comparatively few in them, in their straight 

 regions occasionally types I, II and III, and in the coils a few III. In the mesenteries 

 the mesoglsea is thickened in the region of the wider pleats, thin in the remaining parts. 

 Below the stomodseal region of the polyp, the entocoelic pleats extend over the greater 

 part of the width of the mesentery. 



The endoderm of the oral-disc is not so thick as the ectoderm over it, but has 

 abundant algse; that of the body -wall is thin above the enterostome but towards the base of 

 the polyp becomes highly reticulated, swollen and transparent with the nuclei arranged 

 along its periphery. The endoderm of the tentacle is thinner than the batteries, with 

 conspicuous vacuoles giving it a somewhat lobulated appearance, and algae are scarce. The 

 mesenterial endoderm is only slightly thickened behind the filament ; algae are compara- 

 tively few, being more numerous in the pleatal region on the exocoelic side and in the non- 

 pleatal region on the entocoelic side. In one of the polyps scattered nematocysts II occur 

 in the endoderm, some of them incompletely formed. Ripe ova are present in three 

 of the polyps in longitudinal rows of from 1 to 5 in every mesentery ; immature ova 

 occur in the endoderm surrounding the eggs. 



Polyps examined, four, 1 from a specimen from Hulule whose corallum is identical 

 with Gardiner's example of F. denticulata, 2 from a specimen from Hulule whose corallum 

 resembles Gardiner's example of Astrcea okeni and Ed. and H.'s F. amplior, 1 from an 

 edge specimen from Minikoi. 



B. Corallum. In the Paris Museum Favia doreyensis, Ed. and H., and Favia 

 urvilleana, Ed. and H., are each represented by a single type-specimen, measuring 

 7*5x6 x5cm. (PI. 22, fig. 8) and 8 x 5 x 4-5 cm., both from Port Dorey ; in the latter 

 paliform lobes are inconspicuous. The single specimen (10x9x6 cm.) from Mers 

 d'Amerique, the type of Favia rotulosa, Ed. and H., is identical with some of my 

 specimens and was doubtless Lamarck's type of Astrea rotulosa (PL 32, fig. 4). In 

 Lamarck's collection is a specimen 7 x 6 x 2'5 cm. from Mers d'Amerique originally named 

 Astrea ananas by Lamarck, which Milne Edwards and Haime have later made the type of 

 Favia ananas. Its corallites are often irregularly compressed, one side projecting more 

 than the other, columella and paliform lobes well developed, a cycle of smaller costae 

 alternating with the main ones, sometimes represented by rudimentary septa within 

 coraUites, in general appearance resembling Gardiner's examples of Orbicella laxa and 



