QUEENSLAND AND THE NEW HEBRIDES. 323 



section, frequently contains nematocysts, and is double above the level o£ the 

 mouth. The endoderni is narrow and contains numerous zooxanthellse and 

 nematocysts. Both parieto-basilar and longitudinal retractor muscles are 

 well developed, the latter on plaitings of the mesogloea (PI. 45. fig. 14, 

 jJ.b.m. & l.m.). The digestive endoderni present on the mesenteries in the 

 proximal region is not so thick as in Z. sandvicensis. It contains many 

 nematocysts, and is loaded with pigmented granules to such an extent that 

 the whole endoderm is often of a bright yellow-brown colour left unstained 

 by the carmine. 



Gonads. — All the polyps cut are fertile and contain ova only. 



Parasites. — A dark brown encysted parasite, probably protozoan, is present 

 in numbers in some of the basal canals. 



The abundance of yellow-brown pigment present in Z. pigmentatus is very 

 striking. At the same time zooxanthellse are as abundant as in Z. sandvicensis 

 and Z. similis, in which species there is very little pigment. It seems, 

 therefore, that the relationship between zooxanthellffi and pigment-granules, 

 in virtue of which they replace one another in the genus Parazoantlms and in 

 several families of Actinaria (Duerden, 9), does not exist in these species. 



Z. pigmentatus resembles Z. sociatus (McMurrich, 4) in size, shape and 

 colour, in its irregular mode of growth and in its stolon. Professor 

 McMurrich, however, to whom I have submitted specimens, has no hesitation 

 in describing it as distinct from his species. He also, with great kindness, 

 sent specimens of Z. sociatus for comparison. 



The globular cavities in the mesogloea are present also in Z. Solanderi (8), 

 but confusion between Z. Solanderi and Z. pigmentatus is impossible. 

 Z. pigmentatus can be readily distinguished from all species hitherto described, 

 by the pigment zone, the sphincter muscle, the structure of the column-wall, 

 and by the irregular incrustation in the proximal half of many of the polyps, 

 all other species of this genus having the mesogloea proper of the column-wall 

 unincrusted. 



G-EMMAEIA ARENACEA, Sp. n. (Pls. 43, 45. figS. 16-20.) 



Forrn (PI. 43. fig. IG). — The polyps, erect, cylindrical, rigid and very 

 gritty, arise from a freely developed, tough, and very thick coenenchyme. 

 They are of equal diameter throughout. The capitulum, marked by some 

 28 to 29 ridges, is not swollen in retraction. The young polyps present 

 arise from the ccenenchyme, not from the bases of other polyps. The surface 

 is thickly covered with adhering sand grains, which form a crust largely 

 concealing the deep transverse wrinkles of spirit-specimens. Both column 

 and coenenchyme are overgrown with patches of Rividaria and Lynghya, 

 two genera of the Cyanophyceas, from which the ridges of the capitulum arc 

 more or less free. 



